We used a cake mix to make the crust for this creamy chocolate dessert from the former Chocolate Cafe and Coffee House in Missouri. It makes 24 bars so it's perfect for a potluck or office party.
In a medium bowl, stir together 1 egg and 1/2 cup melted butter. Stir in dry cake mix until combined (You may need to work the mixture together by hand, as it will be thick). Press evenly into the bottom of a greased 13x9x2-inch baking pan pan. Bake in a 350° oven for 15 minutes.
Meanwhile, in a large mixing bowl, beat cream cheese with an electric mixer until fluffy. Add 2 eggs, one at a time, beating on low speed after each addition just until combined. Gradually add 16 ounces powdered sugar, 1 cup at a time, beating on low speed until smooth. Slowly add 1/2 cup melted butter, the chocolate topping, coffee and vanilla, continuing to beat on low speed until just combined. Pour batter over baked cake crust.
Bake for 35 minutes more (center will not appear to be set). Cool completely in pan on a wire rack before cutting into bars. If you like, sprinkle with additional powdered sugar. Cut into bars.