Preheat oven to 350° F and grease an 8x8 square baking dish with butter or spray oil.
Add the flour, brown sugar, white sugar, and cinnamon to a small mixing bowl and mix together.
Add the diced cold butter to the flour mixture and cut it into the flour mixture using a fork or two knives. Make sure all of the flour and sugar mixed and it becomes moist and crumbly. I have even used my hands.
In a medium mixing bowl, combine the flour, sugar, baking powder, cinnamon and salt and mix well.
Add the butter to the dry ingredients and blend well.
Add the milk, egg, and vanilla extract and stir until just barely blended.
Pour half of the cake batter into the baking dish and sprinkle a thin layer of the crumb topping across the batter.
Then pour the remaining batter in and spread evenly.
Top with the remaining streusel topping and again spread evenly across the top.
Bake for 40 minutes or until a toothpick comes out clean when inserted into the center.
Cool for 5-10 minutes before slicing into 9 squares.
