Preheat oven to 350°. Spray a 9” square pan with cooking spray.
Whisk flower, baking powder, and salt together in a medium bowl.
Mix sugars, butter, peanut butter, and egg in a large bowl. Stir in milk. Stir dry ingredients into wet and stir until just combined.
Make the crumb topping: stir together brown sugar, flour, cinnamon, and melted butter. Fold in chocolate chips.
Place half the cake batter in the pan and spread to fit. Top with half the streusel. Repeat with remaining cake batter and streusel. Bake for 21-24 minutes until a toothpick comes out clean. (Mine took 22 minutes to bake.)