In a tall cup or jar, add the egg yolks and lemon juice. Use an immersion blender to combine them.
VERY SLOWLY drizzle the bacon grease in with the egg yolks and lemon juice, continuing to blend the entire time. As you are blending in the bacon grease, the mixture should begin to thicken and turn a light color.
Notes
Nutrition info for one serving (about 1 tbsp): 109 calories, 12g fat, 0g carbs, 0g protein. Special notes: If you don't have a full cup of bacon grease, you can use avocado or olive oil to make up the difference. Also, if you don't have an immersion blender, you can use a food processor or blender, as long as you can add liquid while it is blending.