Baked Oatmeal with Apples

Bahan-bahan (6 porsi)

• 2 cups old-fashioned rolled oats ((not instant))
• ¾ cup (packed) light brown sugar
• 1 cup chopped walnuts or pecans, (divided)
• ½ cup raisins
• 1 teaspoon baking powder
• 2 teaspoons cinnamon
• ½ teaspoon salt
• 2 large eggs
• 2 cups milk
• 1 teaspoon vanilla extract
• 4 tablespoons unsalted butter, (melted, plus more for greasing the dish)
• 2 tart yet sweet baking apples, (such as Honey Crisp, peeled and cut into ½-inch (1.3-cm) chunks (about 2 cups/232 g))