Double Chocolate Gooey Butter Cake

8 tablespoons (1 stick) butter, melted, plus
    8 more tablespoons (1 stick) butter, melted,
1 (18.25 ounce) box chocolate cake mix
3 eggs, divided
8 ounces cream cheese, softened
3 to 4 tablespoons cocoa powder
1 (16 ounce) box confectioners' sugar
1 teaspoon vanilla extract
1 cup chopped nuts

Heat oven to 350 degrees F. Lightly grease a 13 x 9-inch baking pan.

In a large bowl, combine the cake mix, 1 egg and 1 stick melted butter, and stir until well blended. Pat mixture into prepared pan and set aside.

In a stand mixer, or with a hand mixer, beat the cream cheese until smooth. Add the remaining 2 eggs, and the cocoa powder. Lower the speed of the mixer, and add the confectioners' sugar. Continue beating until ingredients are well mixed. Slowly add the remaining 1 stick of melted butter and the vanilla extract, continuing to beat the mixture until smooth. Stir in nuts with a rubber spatula. Spread filling over cake mixture in pan. Bake for 40 to 50 minutes. Be careful not to over-bake the cake; the center should still be a little gooey when finished baking.

Let cake partially cool on a wire rack before cutting.