In medium bowl, mix 1/2 cup of the brown sugar, nuts, the butter and vanilla; spread in crust. In another bowl, beat pumpkin, cream cheese and remaining 2 eggs and 3/4 cup brown sugar with electric mixer on medium speed. Beat in flour, cinnamon, ginger, allspice and nutmeg. Spoon over nut mixture. Bake 15 minutes. Reduce oven temperature to 350°F; bake 30 minutes longer or until set. Cool. Garnish with whipped cream and additional nuts.