Instructions

1. Place 1 cup of the rolled oats and 1 cup milk in a large bowl and stir to combine. Let sit for 20 minutes.
2. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 400ºF. Line a standard 12-well muffin tin with paper liners or coat with cooking spray. Place 1 1/2 cups all-purpose flour, 1/2 cup packed brown sugar, 1 teaspoon ground cinnamon, 1 teaspoon baking powder, and 1/2 teaspoon baking soda in a medium bowl and whisk to combine.
3. Melt 1 stick unsalted butter if using in the microwave or on the stovetop. Add the butter or 1/2 cup vegetable or canola oil, 1 large egg, 1 tablespoon vanilla extract, and 3/4 teaspoon kosher salt to the oat mixture and whisk until combined.
4. Add the flour mixture and fold with a flexible spatula until almost combined with a few streaks of flour left. Scatter 1 1/2 cups fresh or frozen blueberries over the batter and continue folding until the blueberries are evenly distributed and there are no streaks of dry flour left.
5. Divide the batter evenly among the muffin wells (about 1/3 cup per well), they will be very full. Sprinkle with the remaining 1 tablespoon rolled oats, about 1/4 teaspoon per well.
6. Bake until golden brown on top and a tester inserted into the center of a muffin comes out clean, 20 to 22 minutes. Let cool for 5 minutes in the pan. If not using paper liners, run a thin knife around each muffin to loosen. Transfer the muffins to a wire rack and let cool for at least 15 minutes before serving.