Place a Dutch oven or other large, heavy bottomed pot over medium-low heat. Add the olive oil and then the bacon. Fry, stirring occasionally until the bacon is crisp, about 10 minutes, then remove it with a spatula and set aside.
Add the leeks, garlic and cayenne pepper to the same pot and fry, stirring frequently until the leeks are translucent, about 5 minutes. Add the potatoes and the broth, stir together and increase the heat to medium. Simmer without the lid until the potatoes are fork tender, about 15- 20 minutes.
Add the corn and red pepper, stir and cook until the corn is hot, about 5 minutes. Then stir in the cooked bacon.
Reduce the heat to low, then stir in the prawns and let them cook just until opaque, about 2 minutes. Pour in the cream, salt, pepper and ½ cup of the green onions. Stir and season with additional salt and pepper to taste.
Serve while hot, garnishing the top of each soup with the remaining sliced green onions.
Notes
Don't cook the chowder for too long after adding the prawns or they can become overcooked and tough.