Smear the bottom and sides of the pan with the butter. Pour in the eggs and set over moderately low heat. Stir slowly and continually, reaching all over the bottom of the pan. Nothing will seem to happen for 2 to 3 minutes as the eggs gradually heat. Suddenly they will begin to thicken into a custard. Stir rapidly, moving pan on and off heat, until the eggs have almost thickened to the consistency you wish. Then remove from heat, as they will continue to thicken slightly.