Place the 4 egg yolks, lemon juice, salt and pepper in a bowl. Place that bowl in a larger bowl of luke warm water. (This gets the chill off the eggs) Put the 2 sticks of butter in a measuring cup. After about 5 minutes, empty the egg yolk mixture into a blender. Melt butter in microwave until hot, about a minute. Run blender on high and slowly add the melted butter. Sauce will thicken.