Heat 2/3 cup brown sugar, 1/3 cup milk, and chocolate in double boiler until chocolate is melted. Cool thoroughly. Cream shortening and 2/3 cup brown sugar. Add eggs; beat well.
Sift dry ingredients and add alternately with 1/2 cup milk. Add vanilla and chocolate mixture.
Fill paper-lined cupcake pans 1/2 full. Bake in moderate oven (375 degrees) for about 20 minutes.
Frost with "Chocolate Fudge Glaze." Makes about 18 cupcakes.