Oysters Mornay (Baked Oysters With Cheese)

Name: Oysters Mornay (Baked Oysters With Cheese)
Prep time: 20 min
Cook time: 6 min
Total time: 26 min
Ingredients: 12 Oysters (on the half shell or shucked) (12 large oysters or 24 small oysters); 3 tbsp Butter; 2 tbsp All purpose flour; 1 c Chicken broth; 1 c Half and half cream (10% - 18% M.F.); 1 Egg yolk; 1 tsp Lemon juice; 1/2 c Swiss cheese, shredded; 1/4 c Cheddar cheese, shredded; Optional: Paprika, fresh ground black pepper, lemon wedges.

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Last Updated on November 3, 2022 by Sabrina Currie

Oysters Mornay are a French classic. Fresh oysters get baked in a flavorful, creamy sauce with swiss cheese for a decadent and easy appetizer and it's done in under 30 minutes!

A fork with a piece of cheesy baked oyster lifted out of a white ramekin. It is a creamy yellow color with bubbly black and brown spots on top.

Mornay sauce is a rich French cheese sauce. Traditionally made with Swiss or Gruyere cheese and a little Parmesan cheese, I've used cheddar instead of the Parmesan in this recipe. This is a popular sauce for topping eggs and vegetables like asparagus too. (If you have extras, try them raw with this oyster vinaigrette sauce!)

This was inspired by my Miso Baked Oysters on this site, and pairs well with Crispy Japanese Fish Katsu or Easy Seafood Alfredo and a crisp Apple Kale Slaw for a special seafood dinner.

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Ingredients
Instructions
Substitutions
Variations
Equipment
Storage
Top tip
FAQ
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Ingredients

Oyster Mornay is a classic French preparation but don't be scared off, it's actually really easy and doesn't take too many ingredients.

Oysters - Shucked oysters or oysters in their half shell will both work great for this. If you have a tub of frozen oysters in your freezer, they will be perfect for baked oysters too. Pull them out to thaw in the fridge overnight. Large or small are fine. If the oysters are large, I like to slice them into large, bite sized pieces before baking.
Swiss Cheese - Labelled Swiss or Emmenthal/Emmental or gruyere will give you this traditional flavor. Grated works best so it can melt in evenly.
Cream - I've used 10% M.F. or half and half cream. You can use heavier cream for a slightly thicker result or lighter cream for a thinner sauce. I don't recommend using regular milk because you won't get the rich melty sauce texture that this is supposed to be.
Flour - Plain flour, aka all purpose flour is perfect for this recipe.

See recipe card for quantities.

A platter of creamy grey oysters on their white half shells with grey and purple edges on the shells.

Instructions

To make this easy recipe, first make the Mornay sauce, then spoon on top of shucked oysters and broil until golden brown and bubbly. Easy, right?! (Also, if you are looking for what to serve with these, check out the top 50 side dishes to serve with oysters.)

Note: This recipe makes more sauce than you will need for the oysters. You can double the oysters to make 24 servings of oysters if you've got a big crew, or save the extra sauce to pour over vegetables for a fancy veggie side dish.

Stainless steel pot with butter starting to melt and a small pile of flour on one side.

Step 1. Set a heavy bottomed, small or medium-sized saucepan over medium heat. Melt butter and add flour. Cook, stirring until butter and flour (roux) is well blended and bubbling. About 1-2 minutes.

Note: Salted or unsalted butter is fine for this recipe.

Pale yellow sauce in pot looks smooth and runny with a red silicone whisk in it.

Step 2. Remove from heat and add stock all at once, whisking quickly to incorporate well and prevent lumps. Return to heat, stirring frequently until thickened and mixture boils. Reduce heat to low as soon as it starts to boil.

Cream being poured into the roux and stock mixture.

Step 3. Add cream (reserve 1 tablespoon for the next step) to the sauce in the pot and stir until cream is heated through, about 2-3 minutes.

A measuring cup has egg yolk and a tablespoon of cream in it, not yet mixed.

Step 4. In a small bowl, whisk egg yolk with 1 tablespoon of the cream and set aside.

Hot white bechamel sauce being slowly poured into the measuring cup with the egg yolk in it.

Step 5. Slowly add a ladle of hot cream sauce to the egg yolk, whisking constantly. This will temper the egg yolk so it mixes in without getting lumpy. Once it's been incorporated, pour the yolk mixture into the hot sauce and mix well.

Sauce is creamy light yellow and looks thick and smooth. Grated orange cheddar is on top.

Step 6. Add lemon juice, whisk and then add both kinds of cheese. Stir once, then let melt, stirring occasionally.

Sauce is creamy and smooth, pepper is sprinkled on top.

Step 7. Season with salt and pepper if desired. Mornay sauce is finished.

A large oyster on a cutting board has been sliced into 4 equal pieces.

Step 8. Pre heat broiler or oven to 500'F.
Prepare oysters. If large, cut into bite-size pieces and return to half-shell or place oysters in ramekins.

5 ramekins on a baking sheet have oysters in them.

Step 9. One large or 2 small oysters per ramekin or one oyster per shell. Place all shells or ramekins on a baking sheet.

Ramekins of oysters have been filled ¾ full with creamy sauce and sprinkled with red paprika.

Step 10. Spoon sauce over oysters to cover. Sprinkle lightly with paprika if desired.

Baking sheet of oyster filled ramekins placed in the oven under a broiler.

Step 11. Place baking sheet of oysters in the oven under the broiler.

Oysters in ramekins under broiler are brown and bubbly on top.

Step 12. Broil 4-6 minutes until starting to brown. Set the timer so you don't forget about them! Turn broiler off and let oysters cook 1-2 more minutes before removing from oven.

3 oyster shells on salt on a black baking sheet with a bubbly yellow and browned sauce and oysters inside.

Tip: If you are baking oysters in the shell, pour rock salt on the baking tray to set the oyster shells in so they stay up without tipping over.

Finished baked oysters mornay served with lemon wedges and lettuce leaves. Served with glasses of white wine.

Serve while warm with crusty bread and extra wedges of lemon or hot sauce.

Substitutions

Cheese - Any meltable cheese will work for the Mornay sauce but be sure you like the flavor of it with the oysters. Cheddar, fontina and gruyere are all great. See the FAQ section below for more options if you want to add some stronger flavors.
Broth - Vegetable stock or fish stock can both be used. Sometimes fish stock can be strong or less available. Chicken stock with any oyster liquor from the oysters is what I like to use.
Vegetarian- As a mom of some vegetarians, I am often making swaps so the whole family can enjoy my recipes. By using veggie stock in the sauce, you can fill a ramekin with some bite sized vegetables (asparagus, leeks and spinach are all delicious), top with sauce and bake it up for the vegetarians at the table. I also like to use leftover Mornay sauce this way later in the week for a vegetable side that elevates Friday night steaks.

Variations

Bacon Cheddar Baked Oysters - Use all cheddar cheese instead of Swiss and add 5 dashes each of Worcestershire and Tobasco sauce (or a pinch of cayenne) instead of the lemon juice in the Mornay sauce. Add a teaspoon of cooked bacon bits to each oyster before spooning sauce over and baking oysters as per recipe.
Florentine - Spoon 1-2 tablespoons of cooked and drained spinach underneath the oysters before topping with sauce and broiling as per the recipe. (This is my favorite way to eat my oysters Mornay. Spinach makes it healthy, right?!)
Seafood Mornay - Swap out the oysters for a mixture of your favorite seafood. Any bite sized bits will work. Shrimp and scallops, salmon or cod. Add in a little chopped parsley for more color and enjoy.

Love a good, baked seafood recipe? You've gotta try my Roasted Miso Glazed Salmon, it's always a crowd favorite and so easy too.

Equipment

No special equipment here. No ramekins? Use the oyster shells or other oven proof dish. No broiler? Turn your oven up hot, to 500'F and bake an extra 1-2 minutes until bubbly and brown or bake them in a hot BBQ/Grill.

Storage

Like all seafood, these are best the day they are made but leftovers can be safely stored, covered in the refrigerator for 2 days after baking. Reheat in microwave or oven until hot. (Be careful of splattering sauce in the microwave. Cover with parchment or other cover when microwaving and wait 2 minutes before uncovering and enjoying.)

Extra Mornay sauce will keep well in the fridge for up to 6 days. Keep covered of stored in an airtight container and reheat over low heat, stirring frequently.

This finished recipe doesn't freeze well once made though you can freeze the components separately. Fresh, shucked oysters freeze well if stored in an airtight container as does the Mornay sauce.

Mornay sauce may separate when thawed. This can be fixed during reheating. To reheat Mornay after freezing, bring it to room temperature, then slowly reheat it in a heavy bottomed pot over low heat, stirring frequently. Add in a tablespoon of broth or butter if sauce seems too thick, and whisk in well.

Grey countertop with a rectangle white serving board topped with 5 ramekins of oysters mornay, lemon wedges, lettuce leaves, Tobasco sauce and glasses of white wine.

Top tip

I love adding a big squish of lemon to the sauce. While not added traditionally, it will keep your Mornay sauce from becoming grainy or stringy and adds a pleasant tang. While you can use a teaspoon of bottled juice, as always, a squirt of fresh lemon juice adds delicious, bright and natural flavor.

FAQ

Can I use different cheese for Mornay sauce?

Yes! Traditional Mornay sauce uses Swiss cheese (Emmental or Gruyere) and a little Parmesan but you can use any cheese you like as long as it melts well. Cheddar is particularly good, as is fontina, muenster, Monterey jack, Havarti, and provolone. Try smoked gouda for a smoky twist or go bold with Taleggio or a blue cheese like Cambazola if you like a little funky flavor.

What are Mornay oysters?

These are simply oysters that have been baked or broiled with Mornay sauce on top. They are similar to the Japanese Oysters Motoyaki, oysters Florentine and oysters gratin in that these all have a creamy sauce.
Mornay sauce is a bechamel sauce flavored with swiss cheese and enriched with egg yolk. It bakes up bubbly and brown and pairs well with briny oysters.

How do you store live oysters?

Live oysters should be stored in your fridge until ready to eat or cook. Keep them in a plastic bag with holes so they can breathe but not get dried out. Before shucking, give them a rinse or a scrub in the sink to remove any loose dirt or shell.

How do you cook oysters Mornay?

Prepare oysters in their half shell or in ramekins. Cook the Mornay sauce separately, then top the oysters generously with the sauce. Place in oven, BBQ or under the broiler and bake/broil for 6-10 minutes until brown and bubbly.

See more Oysters →

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A fork with a piece of cheesy baked oyster lifted out of a white ramekin. It is a creamy yellow color with bubbly black and brown spots on top. Text box on top half of photo with recipe title, baked oysters mornay.

If you have any questions or comments, you can find me on Instagram, Pinterest and Facebook. I try to answer any recipe related questions quickly as I know you might be in the middle of making it.

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Cheers and happy cooking, Friends! Sabrina