Turn the food processor on low (or use a stick blender on low) and slowly drizzle the liquid bacon fat into the yolk mixture, drop by drop in the beginning. If you put too much oil at once, it will separate.

As you add more bacon fat, the emulsion will form and the mayonnaise will start to thicken and you can pour the fat in faster.

Once you add all the bacon fat, and add the mustard and taste your creation. Add salt to taste if needed.

Store in the refrigerator.