Easy Blender Hollandaise Sauce

3 egg yolks
1 tablespoon lemon juice
1 teaspoon dry mustard
1 cup (2 sticks) butter, melted and hot

In a blender or food processor, blend egg yolks, dry mustard, and lemon juice. While on high speed, add melted butter, beginning with just a few drops at a time and increasing to a steady stream as mixture thickens. Serve immediately.