Lidey's Maple Walnut Baked Oatmeal

• 3 Tbsp. melted unsalted butter, slightly cooled, plus extra for the baking dish
• 3/4 cup walnut halves, coarsely chopped
• 1 1/2 cups rolled oats, such as Quaker
• 3/4 cup oat bran
• 2 tsp. cinnamon
• 1/8 tsp. nutmeg
• 1 tsp. baking powder
• 1/2 tsp. kosher salt
• 2 1/2 cups low-fat milk (I used 1%)
• 1 large egg
• 1 tsp. vanilla extract
• 1/3 cup maple syrup
• 3/4 cup Candied Maple Walnuts (see below)
• Vanilla Greek yogurt and fruit, for serving

Candied Maple Walnuts

• 3/4 cup walnut halves
• 1/4 cup maple syrup
• pinch of kosher salt