For Cake: Heat Oven to 350 degrees. Coat an 8x8x2 inch baking pan with nonstick spray
In a large bowl, whisk together flour, sugar, baking powder and salt.
In a small bowl, whisk together egg, milk, oil and vanilla
Make a well in the center of flour mixture. Add egg mixture to well and beat with a spoon 1 minute, until evenly moistened; stir in chocolate chips. Spoon into prepared pan and top with Aronia Berries.
For Topping: In a small bowl, combine flour and sugar. Cut in butter with pastry blender until crumbly. Stir in walnuts. Sprinkle over Aronia Berries
Bake cake with topping at 350 degrees for 35 to 40 minutes or until wooden pick inserted in center comes out clean. Cool pan on a wire rack. Cut into 9 squares