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