In a medium bowl mix the oats, almonds, baking powder, cinnamon, nutmeg, and salt together.
In another bowl or in a liquid measuring cup, whisk the milk, vanilla, egg, maple syrup and coconut oil (or butter) together until smooth. It's ok that the coconut oil/butter will solidify and form small clumps. It'll work itself out in the warm oven, promise.
Pour the wet ingredients over the oatmeal mixture and stir to combine.
Lightly grease a 9X9-inch baking dish (can use a similar sized baking dish of any shape - 9X9-inch or larger but smaller than a 9X13-inch).
Toss the blueberries over the bottom of the dish. Give the oatmeal mixture a final stir and pour over the top of the blueberries (if using frozen blueberries, the oatmeal will definitely take on more of a blue-ish hue than if using fresh). Cover with plastic wrap and refrigerate overnight (8-12 hours).
In the morning, preheat the oven to 350 degrees, uncover the baking dish and bake for 55-60 minutes until the mixture is set and oats are tender but still slightly chewy. Stir to combine, if desired, or just scoop out in portions as is.
Serve with additional milk (to stir into the oatmeal), if desired.
Adaptable: this recipe is so, so adaptable. Omit the blueberries and use apples or bananas. Sub in walnuts for almonds (and consider lightly toasting the nuts beforehand). Take out the fruit and nuts altogether and bake just the oats in the creamy, custardy mixture. Seriously, the options are endless. Sweeteners: you can try using other sweeteners besides the maple syrup (brown sugar, maybe, or agave nectar?).Milk: also, you could certainly use regular milk for the almond, if desired.