Homemade Mayo

4.25 from 8 votes

Pour the oil into a wide-mouth glass jar with an opening a little bit wider than the head of your immersion blender. Crack the egg into the oil and let settle unto the bottom of the jar.
Place the immersion blender into the jar and position the blade directly over the egg yolk. Turn the immersion blender on low and hold in place, while the blender is running, until the bottom of the jar starts to turn into a creamy emulsion, about 10 seconds.
Once you see that creamy emulsion at the bottom, start lifting the blender up a bit and pressing it back down, essentially emulsifying the mixture above the mayo at the bottom, bit by bit, until you reach the top and the entire jar is emulsified.
Use as-is as a base for dressings or you can also turn it into an actual mayo by blending in the additional ingredients listed above.

If your egg is chilled, place it in a cup of hot or very warm water for 3-5 minutes to bring it to room temp. *YOUR EGG MUST BE AT ROOM TEMP OR YOUR MAYO WILL NOT EMULSIFY*
Place room temp egg, the mustard powder, the kosher salt, and 1/4 cup of the oil in a food processor or blender, blend until well combined.
Now, for the main event...turn your food processor or blender on and keep that blending as you VERY SLOWLY pour in the remaining 3/4 cup of the oil in. When I say slowly pour, just keep a constant flow going as slow as you can possibly go. The slower you pour, the thicker your mayo will come out! If you pour too quickly, it will not emulsify and you'll just have a sloshy mess.
When you are done and you have a beautiful, fluffy mayo; squeeze in the juice of the lemon and pulse one more time to combine.