Mix chocolate, flour, and sugar in heavy saucepan.
In another bowl, separate the egg yolks from the egg whites. Refrigerate the whites for use later. Slightly beat yolks in another bowl and add milk. Combine yolk mixture with dry ingredients in saucepan.
Stir consistently over medium heat until thick. Then add butter and stir until mixture contains no lumps.
Pour into baked pie shell and put into oven until mixture bubbles.
Beat egg whites until stiff and add 3 tablepoons of sugar. Put on pie and put back into oven until slightly brown.