Preheat oven to 375 degrees F. Combine biscuit mix and brown sugar, and cut in margarine till crumbly. Add chopped nuts. Press into a 9x13-inch baking pan. Bake 10 minutes. Cool. Cream powdered sugar and cream cheese till fluffy. Fold in whipped cream. Spread mixture over baked crust. Pour milk into bowl. Add pudding mix and beat till well blended. Pour over cream cheese layer. Refrigerate. If desired, garnish with whipped cream and green cherry.