Ingredients
1 {egg} yoke
1/2 teaspoon lemon juice or vinegar
2 pinches salt
1 pinch cayenne
3 tablespoons butter
Method
Combine yolk & juice with salt and pepper in a double boiler, beat butter into egg mix one tablespoon at a time. Cook over low steam until thickened, using a whisk. If separates, beat in 1 teaspoon boiling water.