Heat oven to 350°F. Grease 9-inch pie pan. In large bowl, combine flour, brown sugar, baking powder, 1/2 teaspoon salt, mace and dash of cinnamon; mix well. Stir in 1 1/2 teaspoons vanilla and eggs; blend well. Add apples and walnuts; mix well. Pour into greased pan.
Bake at 350°F. for 20 to 30 minutes or until browned and firm to the touch.
Meanwhile, in small bowl, combine all hard sauce ingredients. Beat at high speed until well blended. Shape into 2-inch-thick roll. Wrap in plastic wrap; refrigerate until firm.
To serve, cut hard sauce into slices. Top each serving of dessert with slice of hard sauce.