Preheat oven to 350 F. Whisk together the flour, baking powder, and salt in a medium bowl. Cream the butter and sugar until light and fluffy. Beat in the eggs and vanilla. Gradually add the dry ingredients to the wet and stir until combined.

Spread the 2/3 of the batter in a greased 9 x 13 inch baking dish. To make the cinnamon layer, stir together the sugar and cinnamon. Sprinkle the cinnamon mixture on top of the batter in the pan. Drop the remaining batter in teaspoon sized amounts over the cinnamon sugar mixture.

Bake at 350 F for 20-24 minutes or until a toothpick inserted comes out clean. Let cool completely.

To make the glaze, combine the powdered sugar, vanilla, and enough milk to make a smooth consistency. Drizzle over cooled bars. Store tightly covered on the counter for 2 days or freeze for longer storage.