Grease an 8x8x2 inch baking pan; set aside.

For streusel topping, in a small mixing bowl combine the 1/4 cup flour, the 1/4 cup brown sugar, the 2 tablespoons peanut butter and the 1 tablespoon butter. Stir together until crumbly. Sstir in the 1/4 cup chocolate pieces. Set topping aside.

In a large mixing bowl beat the 1/4 cup peanut butter and the 2 tablespoons butter with an electric mixer on medium to high speed for 30 seconds or until combined.

Add about half of the 1 cup flour, the 1/2 cup brown sugar, half of the milk, the egg, baking powder, baking soda, and salt. Beat with an electric mixer on low speed until thoroughly combined, scraping the sides of the bowl constantly. Add the remaining milk. Beat on low to medium speed just until combined. Stir in the 1/4 cup chocolate pieces.

Sspread batter evenly in the prepared pan. Sprinkle with the streusel topping. Bake at 375 oven for 25-30 minutes or until wooden toothpick inserted near the center comes out clean. Cool on a wire rack for 15 minutes. Cut into squares. Serve warm. Cover any leftovers and store at room temperature or in the refrigeraator up to 3 days. Makes 1 cake.