Cinnamon Brown Sugar Pop-Tarts Ingredients For the pastry: 2 1/2 cups all-purpose flour 1 teaspoon salt 2 sticks (1 cup) unsalted butter, cold, cut into small chunks 4 tablespoons ice water, plus more if needed For the filling: 1/2 cup brown sugar 2 teaspoons ground cinnamon 1 tablespoon all-purpose flour 1 large egg, whisked