Step 1

Place the egg yolks, lemon juice, vinegar, salt, and mustard in a jar and blend using an immersion blender until combined and slightly thick. This takes about 30 seconds.

Step 2

SLOWLY stream in the avocado oil into the mixture a little at a time while blending continuously using the immersion blender. You may have to move the blender up and down within the jar to incorporate the oil. It should start to thicken immediately.

Step 3

Keep going until you've added 1 cup of oil and then give it a good stir with a spatula. It should be VERY thick.

Step 4

Transfer to a lidded container and refrigerate.