Apple Bars

Bahan-bahan (12 porsi)

• 1 cup whole wheat flour
• 1 cup all-purpose flour ((plus 3 tablespoons), divided)
• 1 cup old-fashioned rolled oats
• 1 cup packed dark brown sugar
• ½ teaspoon baking soda
• ½ teaspoon ground cinnamon
• ½ teaspoon kosher salt
• ⅛ teaspoon ground allspice
• ⅛ teaspoon ground nutmeg
• 10 tablespoons unsalted butter
• 2 cups peeled diced firm apples (such as Granny Smith (about 2 large or 3 medium))
• ½ cup homemade or store-bought caramel sauce