Cream butter and sugar in large mixing bowl 2 minutes.

Beat in eggs, vanilla and sour cream.

Mix flour, baking powder and baking soda in a medium-size mixing bowl.

Add flour mixture alternately with orange juice, blending well about 3 minutes.

To make streusel filling, stir all ingredients together until well-mixed. (add 1/2 cup chopped walnuts if you like nuts)

Pour half of batter into a greased 8-inch square baking pan. Smooth batter. Sprinkle with half of the streusel filling; top with remaining batter, spread into a smooth layer. Sprinkle with remaining streusel filling.

Bake in preheated 350°F oven 30-35 minutes or until cake tester/toothpick inserted in the center comes out clean..

Remove from oven; immediately sprinkle with 1/4 cup chocolate chips. Let stand for 2 minutes; spread choclate with knife in swirling pattern.

**In place of choclate chips, you can use Chocolate minichips.