Combine the bacon fat and oil in a one measuring cup and set aside.

In a small metal bowl, use an immersion blender to blend (or whisk by hand) the egg yolks and whole egg until the mixture becomes milky white and frothy.

When you see it change dramatically in color and texture, continue to mix a little longer. (this last bit of whisking is for added insurance, as it's at this stage that it's easy to stop blending too soon, and if the eggs are beaten enough, they cannot support the fat and emulsify into mayo.)

Once the eggs are the desired consistency, begin to slowly add in the oil mixture.

Continue to mix until all the oil is added, about 1 to 2 minutes.

Season with salt and vinegar, and add more to taste as desired.