01 -
Heat your oven to 375°F (190°C) and pop paper liners in your muffin tin.
02 -
In a big bowl, whisk together your flour, granulated sugar, baking powder, and salt until well combined.
03 -
In another bowl, mix your melted butter, eggs, milk, and vanilla. Pour this into your dry ingredients and stir just until mixed.
04 -
Gently fold in the sour cream until your batter looks smooth and creamy.
05 -
In a small bowl, stir together the brown sugar and cinnamon for your swirl.
06 -
Fill each muffin cup halfway with batter, sprinkle with cinnamon sugar, then top with more batter until they're three-quarters full.
07 -
Pop them in the oven for 18-20 minutes. They're done when a toothpick comes out clean.
08 -
While they're cooling a bit, mix powdered sugar and milk for the glaze. Drizzle over your warm muffins.