1 egg yolk
3/4 teaspoon Dijon mustard
1 teaspoon freshly squeezed lemon juice
Sea salt and freshly ground pepper
1/2 cup liquid bacon fat
Combine the egg yolk, mustard and lemon juice in the small bowl of a food processor or in a blender and process to mix. Season with salt and pepper.
Have the bacon fat liquid, but not hot. With the machine running, gradually the bacon fat until the mixture starts to stiffen and emulsify, about 2 minutes. Once it starts to emulsify, you can add the fat more quickly. If the mayonnaise is too thick, just blend in 1 teaspoon of boiling water to thin it. Taste and adjust the seasoning.