Preheat oven to 375 degrees F. In a medium mixing bowl combine flour, baking powder, cinnamon, baking soda and allspice. Set aside.

In a large mixing bowl beat the butter with an electric mixer on medium speed for 30 seconds. Beat in the sugar. Add the egg; beat well. Stir pumpkin and flour mixture into egg mixture with a wooden spoon. Stir in the chopped pecans.

Drop the dough by a rounded teaspoon about 2 inches apart on an ungreased cookie sheet.

Bake cookies in preheated oven for 10 to 12 minutes or until bottoms are lightly browned. Transfer the cookies to wire racks; cool. Frost the cooled cookies with Brown-Sugar Butter Frosting. about 40 cookies.

In a medium saucepan heat 6 tablespoons butter and 1/3 cup packed brown sugar over medium heat until butter is melted. Remove mixture from heat. Stir in 2 cups sifted powdered sugar and 1 teaspoon vanilla. Add enough hot water (2 to 3 teaspoons) to make a smooth, spreadable frosting. Frost the cooled cookies immediately after preparing frosting. If frosting becomes grainy, add a few more drops of hot water and stir frosting until smooth.

Place in layers separated by waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze unfrosted cookies for up to 3 months. Thaw, then frost cookies.