Mix sugar, shortening and egg together thoroughly.
Blend in milk and cooled chocolate.
Blend flour, salt and baking powder and stir in.
Mold into smooth roll about 2 inches in diameter.
Wrap in waxed paper and chill until firm for several hours or overnight.
Heat the oven to 400
With a thin, sharp knife, slice the dough in 1/8 inch slices.
Bake on a lightly greased cookie sheet fir 10-12 minutes.
Cool completely.
Place two cookies together with generous amounts of filling.