Preheat the oven to 375F/190C. Grease a loaf pan (9x5) (or double the amounts and use a square 9x9 baking dish).
Toast the nuts in a heated skillet for 4 to 5 minutes, until fragrant and toasted.
In a medium mixing bowl, whisk to combine the oats, toasted nuts, cinnamon, baking powder and salt.
In another mixing bowl, combine the milk, maple syrup or honey, egg, coconut oil, and vanilla. Whisk until blended.
Arrange 2 cups of the blueberries evenly over the bottom of the loaf pan (no need to defrost frozen fruit first). Cover the fruit with the dry oat mixture, then drizzle the wet ingredients over the oats. Wiggle and shake the loaf pan to make sure the milk moves down through the oats.
Top with the remaining berries. Sprinkle some coconut sugar over oats and blueberries if you’d like some extra sweetness and crunch.
Bake for 42 to 45 minutes, until the top is golden brown. Remove your baked oatmeal from the oven and let it cool for a few minutes.