- Preheat oven to 350°F. Grease and flour a 13 x 9-inch baking pan. Measure out 1 cup of dry cake mix; set aside for topping. Combine remaining cake mix, pudding mix, flour, oil, water, eggs, vanilla extract and butter flavoring. Beat at medium speed 2 minutes. Pour into prepared pan.
- Combine reserved 1 cup cake mix, brown sugar, walnuts and vanilla extract. Add melted butter and mix until crumbly (this mixture is moist). Sprinkle on top of cake batter. Carefully cut through batter with knife to create marbled effect. Bake 30-35 minutes.
- Mix together sugar, milk and vanilla extract and drizzle over cooled cake.
Makes 12 to 16 servings.