Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan and line it with parchment paper, leaving some overhang on the sides to act as handles.

In a large bowl, whisk together the all purpose flour, light brown sugar, granulated sugar, baking powder, and salt.

Add the cold, cubed butter. Using a pastry cutter or your fingertips, cut the butter into the flour mixture until it resembles coarse crumbs.

Take out 1 1/2 cups of the crumb mixture and set it aside for the topping. To the remaining mixture in the bowl, add the large egg and mix until a soft dough forms. Press this dough evenly into the bottom of your prepared baking pan to form the crust.

In a separate small bowl, combine the melted butter, 1 cup of light brown sugar, and ground cinnamon. Stir until it forms a thick, smooth paste.

Carefully spread the cinnamon filling over the crust in an even layer. Then, sprinkle the reserved 1 1/2 cups of crumb mixture evenly over the top of the filling.

Place the pan in the preheated oven and bake for 25 to 30 minutes, or until the top is golden brown and the filling is bubbly.

Remove the pan from the oven and let the bars cool completely on a wire rack.

While the bars are cooling, prepare the cream cheese glaze. In a medium bowl, beat the softened cream cheese until smooth and creamy. Gradually add the powdered sugar, milk, and vanilla extract. Whisk until the glaze is smooth and has a drizzling consistency.

Once the bars are completely cool, drizzle the cream cheese glaze over the top. Let the glaze set for about 15 minutes before using the parchment paper handles to lift the bars from the pan and cut them into squares.