In a medium bowl stir together flour and 1/2 cup cocoa powder; set aside. In a large mixing bowl beat four of the eggs, the 2 cups granulated sugar, 1/2 cup of the chocolate-hazelnut spread, and the melted butter with an electric mixer on low to medium speed until combined. Add flour mixture; stir until smooth. Spread batter in the prepared baking pan; set aside.
Wash beaters. In another large mixing bowl beat the remaining 4 eggs, cream cheese, the 1/3 cup granulated sugar, and the remaining chocolate-hazelnut spread on medium speed until combined. Carefully spread over batter in pan.
Bake for 50 to 55 minutes or until cream cheese layer is firm and set. Cool in pan on a wire rack. Cover and chill before cutting. If desired, sprinkle brownies with additional cocoa powder.