Combine egg yolks, Dijon mustard and lemon juice in a blender. Cover, and blend on high for 1-2 minutes. The mixture will blend and start to lighten.
Reduce blender speed and take out the middle stopped in the center of the lid. Slowly pour in butter in a steady stream while the blender is running. You might get a few spits and spatters.
Continue to mix until sauce has thickened, which will happen within 1 minute.
Add salt and optional hot sauce or white pepper, pulse to blend.
Sauce will be semi-warm from agitation in the blender, but you can heat further by setting the whole blender in large bowl of hot water or place sauce in a double boiler sauce pan on low heat, stirring constantly.
If you’ve tried this recipe, come back and let us know how it was!