Preheat oven to 400 degrees. Cream butter and brown sugar. Add redessertsing ingredients. Mix well. Drop by large tablespoonsful onto baking sheet. Six cookies per sheet. Bake at 400 degrees for 10 minutes. Cool on wire rack and top with fudge.
In heavy saucepan, stir together all ingredients. Boil over medium heat for 3 minutes. Cool slightly; beat to thicken. Spoon onto cookies quickly because fudge sets up fast.
Makes 12 large (4-inch) cake-like chocolate cookies with fudge topping.