Preheat oven to 350°F (175°C). Grease or line a muffin tin with paper liners.
In a small saucepan, melt butter over medium heat. Cook until butter is golden brown and begins to smell nutty, about 5-8 minutes. Set aside to cool.
In a large bowl, whisk together sugar, eggs and vanilla extract. Add cooled brown butter and whisk until combined.
In a medium bowl, whisk together flour, baking powder, baking soda and salt. Add to wet ingredients and stir until just combined.
Stir in oats until just combined. Divide batter evenly among prepared muffin tins, filling each tin about ¾ full. Bake for 18-22 minutes or until a toothpick inserted into the center of a muffin comes out clean.
Let cool in tin for 10 minutes before transferring to a wire rack to cool completely.
Interesting Facts
Browning butter is a simple process that adds a nutty, caramel-like flavor to your muffins.
The muffins are best served warm, with a pat of butter.
These muffins will stay fresh in an airtight container at room temperature for up to 3 days.