In a large bowl, whisk together flour, granulated sugar, and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Drizzle in ice water, mixing until dough forms. Divide dough in half, flatten into disks, wrap, and refrigerate for 30 minutes.

In a small bowl, combine the light brown sugar, cinnamon, and flour. Pour in the melted butter and stir until a thick paste forms. Set aside.

Preheat oven to 375°F (190°C). Grease a 9x13 inch pan. Roll out one dough disk and press it into the bottom of the pan. Spread the filling evenly over the dough. Roll out the second dough disk and place it on top. Seal the edges.

Poke holes across the top dough with a fork. Bake for 25-30 minutes until golden brown. Let the bars cool completely in the pan.

Once cooled, whisk powdered sugar and milk until smooth. Drizzle over the bars, let it set for 15 minutes, then slice and serve.