1Heat oven to 350°F. Grease bottom only of 8-inch square pan with shortening or cooking spray.
2In large bowl, mix 1 cup whole wheat flour, the all-purpose flour, granulated sugar, baking powder, salt and baking soda. Cut in butter, using pastry blender or fork, until mixture is crumbly. Add buttermilk, vanilla and egg; stir until well blended. Stir in chocolate chips. Spread in pan.
3In small bowl, mix streusel ingredients with fork until mixture is crumbly. Sprinkle over batter.
4Bake 35 to 45 minutes or until toothpick inserted in center comes out clean. Serve warm or cool.