- 1 tablespoon all-purpose flour
- 1/2 cup packed brown sugar
- 2 tablespoons butter, softened
- 1/2 cup chopped walnuts
- 2 cups semisweet chocolate chips
- 2 cups all-purpose flour
- 1 teaspoon baking powder
- 1 teaspoon baking soda
- 1/2 teaspoon salt
- 1/2 cup butter, softened
- 1 cup white sugar
- 1 teaspoon vanilla extract
- 3 eggs
- 1 cup sour cream
- 1 1/2 cups semisweet chocolate chips
- For the crumb topping: In a small bowl, combine 1 tablespoon flour, 1/2 cup brown sugar and 2 tablespoons butter. Stir in 1/2 cup nuts and 2 cups chocolate chips. Set aside.
- Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9×13 inch pan. In a small bowl, combine 2 cups flour, baking soda, baking powder and salt. Set aside.
- In a large bowl, cream 1/2 cup butter, 1 cup sugar and 1 teaspoon vanilla until light and creamy. Add eggs one at a time, beating well after each addition. Add flour mixture alternately with sour cream. Beat until smooth. Fold in 1 1/2 cups of chocolate chips.
- Spread batter into a 9×13 inch pan. Sprinkle topping evenly over batter. Bake at 350 degrees F (175 degrees C) for 45 to 50 minutes, or until a toothpick inserted into cake comes out clean. Cool completely.