
Combine milk and oats. Set aside for 20 minutes so the oats puff up and soak up some moisture.
Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or use cupcake liners.
Whisk flour, baking powder, baking soda, cinnamon, and salt together in a large bowl. In a medium bowl, whisk melted butter, honey, egg, and vanilla extract until combined. Pour wet into dry ingredients, add soaked oats and blueberries, and gently fold until combined.
Spoon the batter into muffin liners, filling to the top. Bake for 5 minutes at 425°F, then reduce oven to 350°F and bake another 16-17 minutes until a toothpick comes out clean.
Allow the muffins to cool for 5 minutes in the pan, then transfer to a wire rack to cool completely.
Muffins stay fresh covered at room temperature for a few days, then transfer to the fridge for up to 1 week.