Preheat oven to 375 degrees F. Grease a 9-inch springform pan.

In a medium bowl mix together the 1 1/4 cups flour, 3/4 cups oats, baking powder, sugar, 1/4 cup brown sugar, salt, and cinnamon.

In another bowl add the eggs, 1/4 cup butter, sour cream, and milk, mix together until well blended. Pour the wet ingredients into the dry ingredients, mix just until blended. Pour the batter into the prepared baking dish.

For the crumble - Combined all of the dry ingredients together. Add the 6 tablespoons of softened butter and mix together with a fork or by hand. Sprinkle over the top of the batter.

Place into the preheat oven and bake for 23 to 25 minutes or until a wooden toothpick comes out clean. Remove from the oven and set on cooling rack to cool.