Line bottom and sides of 9-inch round cake pan with 24-inch piece of plastic food wrap, allowing ends to hang over sides of pan.
Spread softened ice cream evenly into prepared pan. Fold ends of plastic food wrap over ice cream. Freeze 2 hours or until firm. Remove wrapped ice cream layer from pan. Keep frozen.
Heat oven to 350ºF.
Combine butter and chocolate in 2-quart saucepan. Cook over low heat, stirring constantly, 3-4 minutes or until melted. Remove from heat. Stir in sugar and eggs; mix well. Add flour, baking powder and salt; mix well.
Spread batter evenly into 2 greased and floured (9-inch) round cake pans. Sprinkle tops with sprinkles. Bake 12-14 minutes or until brownies just begin to pull away from sides of pan. Cool 10 minutes. Run thin knife around edges to loosen. Invert onto cooling racks. Cool completely.
Place 1 brownie layer, sprinkle-side down, onto large flat serving plate. Spread with 2 tablespoons hot fudge topping. Unwrap ice cream layer; place over brownie, pressing gently to adhere. Spread bottom of second brownie layer with remaining topping. Carefully place over ice cream, sprinkle-side up. Press down gently. Cover with plastic food wrap; freeze 5 hours or until firm.
Thaw ice cream sandwich in refrigerator 5 minutes. Cut into wedges.
Variation: Coffee Ice Cream Sandwich Grande: Add 1/2 teaspoon ground cinnamon to flour mixture, substitute coffee ice cream for mint chocolate chip ice cream and substitute 1/4 cup finely chopped walnuts for sprinkles.
For easy cutting, dip knife blade in tall glass of very hot water. Dry with paper towels. Repeat with each slice.