Preheat the oven to 375 degrees. Spray an 8 x 8 baking dish with cooking spray and set aside.

In a large bowl cream together the butter and sugar. Add in the egg and mix well.

In a medium bowl combine the flour, chocolate chips, baking powder, and salt.

Add half the flour mixture to the butter mixture and mix well. Stir in the milk and mix until well combined.

Add remaining flour mixture and mix until well combined. Pour into the prepared pan.

In a small bowl combine the brown sugar, flour, oats, cinnamon, and butter. Use your fingers or a fork and mix into a crumble. Stir in the mini chocolate chips. Sprinkle over top of the batter in the pan.

Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.

Cool then cut into pieces and serve.