Coarsely chop or dice the kimchi and stir it into the mayonnaise. Add the garlic, sugar and sesame oil and whisk it together.
Season to taste with kimchi brine, sugar or a sprinkle of salt to taste.
Notes
If you want your sauce to be smooth, whiz this up in your food processor or blender. Only process it long enough to make it smooth, over processing can make the sauce more runny.