Granny Smith Bars

Ingredients

• ***For the bars:***
• 1 (15-ounce) package pastry for a 9-inch double-crust pie
• 1/3 cup all-purpose flour, plus more for flouring work surfaces
• 1 cup white sugar
• 1 1/2 teaspoons ground cinnamon
• 1/2 teaspoon ground nutmeg
• 3 Granny Smith apples, peeled and sliced
• 3 Gala apples, peeled and sliced
• ***For the topping:***
• 1 cup confectioners' sugar
• 2 tablespoons milk
• 1 teaspoon vanilla extract