Combine milk and oats. Set aside for 20-30 minutes so the oats puff up and soak up some moisture. Melt the butter and let it cooled

Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or use cupcake liners.

Whisk the flour, baking powder, baking soda, cinnamon, and salt together in a large bowl until combined. Set aside. Whisk the melted butter, honey, egg, and vanilla extract together in a medium bowl until combined. Pour the wet ingredients into the dry ingredients, stir a few times, then add the soaked oats (milk included, do not drain) and blueberries. Fold everything together gently just until combined.

Spoon the batter into liners, filling them all the way to the top. Top with oats and a light sprinkle of coconut sugar, if desired. Bake for 5 minutes at 425 then, keeping the muffins in the oven, reduce the oven temperature to 350°F (177°C). Bake for an additional 16-17 minutes or until a toothpick inserted in the center comes out clean.

The total time these muffins take in the oven is about 22-23 minutes, give or take. (For mini muffins, bake 11-13 minutes at 350°F (177°C).) Allow the muffins to cool for 5 minutes in the muffin pan, then transfer to a wire rack to continue cooling.