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 another 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. (if you like nuts, add 1/2 cup chopped walnuts)

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

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

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

** Can substitute chocolate chips with chocolate minichips.