1Preheat oven to 350^. Lightly butter and flour a 13x9-inch pan. Spray is best.
In a large bowl, cream together butter and sugar using an electric mixer. Add eggs and vanilla extract, mix to combine. Add pumpkin. Mix well.
2In a medium bowl, combine flour, baking powder, baking soda, salt, and spices, mix to combine. Slowly add flour mixture to butter mixture, Mix well. If desired, add nuts or raisins; mix until evenly distributed.
3Pour batter into pan, spread evenly. Bake 20-25 minutes or until a toothpick inserted in center comes out clean. Allow bars to cool in pan before topping with fudge frosting.
Combine butter and brown sugar in a saucepan over medium high heat; bring to a boil. Lower heat to medium low and continue to boil for 2 minutes, stirring constantly. Add milk and return to boil, stirring constantly. Transfer mixture to a medium bowl, cook to lukewarm.
Gradually add powdered sugar, stirring until blended well. Beat mixture until thick enough to spread; adding additional powdered sugar if needed. If fudge is too thick, add a little hot water.
Frost cooled bars with warm fudge, let fudge set completely before cutting into squares. Store covered in the refrigerator for 3 days.