Blender hollandaise

1. Put the egg yolks, lemon juice, prepared mustard, and dash of cayenne into a blender container and blend until combined.
2. Heat the butter or margarine in a saucepan until melted and almost boiling.
3. With the blender running, slowly, pour about one third of the hot butter, in a thin stream, into the blender container.
4. Turn the blender on high speed and slowly pour the remaining hot butter, blending until the mixture is smooth and thickened.
5. Makes about 1 cup