Step 1

Melt 8 tablespoons butter in the microwave.

Step 2

In the meantime, add egg yolks, lemon juice, salt, cayenne pepper, and mustard to a wide mouthed mason jar.

Step 3

Remove butter from microwave and let stand about 30 to 40 seconds.

Step 4

Grab the immersion blender and stick it inside the jar.

Step 5

Pour the butter into the egg yolk mixture in a thin stream and begin to blend at the same time. While blending, move the immersion blender up and down, slowly, so to combine everything together, and to thicken. This should only take about 30 seconds.

Step 6

Remove blender and taste for seasonings and flavor; adjust accordingly.

Step 7

If it’s too thick, you can add couple teaspoons of water or lemon juice, and stir with a fork until combined. Sauce will thicken as it stands; stir in more liquid as necessary.

Step 8

Use within 1 to 2 hours of making; refrigerate any leftover sauce after 2 hours of cooking.