Baked Oatmeal

Name: Baked Oatmeal
Ingredients: 2 cups/7 oz/200 g rolled oats; 1/2 cup/2 oz/60 g walnut pieces, toasted and chopped; 1/3 cup/2 oz/60 g natural cane sugar or maple syrup, plus more for serving; 1 teaspoon aluminum-free baking powder; 1 1/2 teaspoons ground cinnamon; Scant 1/2 teaspoon fine-grain sea salt; 2 cups/475 ml milk; 1 large egg; 3 tablespoons unsalted butter, melted and cooled slightly; 2 teaspoons pure vanilla extract; 2 ripe bananas, cut into 1/2-inch/1 cm pieces; 1 1/2 cups/6.5 oz/185 g huckleberries, blueberries, or mixed berries