I made this cookie pie yesterday and it seems to fit the bill. It is called Baker's Mississippi Mud Bars:

1/2 C butter or margarine
3/4 C firmly packed brown sugar
1 egg
1 tsp vanilla
1 C flour
1/2 tsp baking soda
1/4 tsp salt
1 pkg (8 squares) Baker's semi-sweet chocolate, chopped, divided
1 pkg (6 squares) Baker's Pre,ium white baking chocolate, divided
1 C chopped walnuts, divided

Heat oven to 350 degrees. Line 9" round baking pan with foil and grease foil.

Beat butter, sugar, egg and vanilla in lg. bowl w/ electric mixer on med. speed until light and fluffy. Mix in flour, baking soda and salt. Stir in 1/2 ea of semi-sweet and white chocolates and 1/2 C walnuts. Spread in prepared pan.

Bake 25 minutes or until toothpick comes out ALMOST clean. DO NOT OVERBAKE. Remove from oven. Sprinkle with remaining chips. Cover with foil. Let satnd 5 min or until chocolates melted. Swirl with knife to marbelize. Sprinkle with remaining nuts. (You could just top with shaved chocolate to more match the recipe you are wanting). Cool in pan on wire rack until chocolate is firm. Cut in wedges. Store in tightly covered container.

Try it - I think you'll like it!