Brown Butter Oatmeal Muffins

Step 1
Mix together milk and vinegar in a large bowl. Stir in oats and allow mixture to soak for at least 15 minutes.

Step 2
Meanwhile, prepare brown butter. Add butter to a small, light-colored saucepan over medium heat. Cook, swirling pan constantly, until butter is melted and brown bits begin to form on the bottom of the pan, 7 to 10 minutes. Remove from heat and allow to cool slightly.

Step 3
Preheat the oven to 375 degrees F (190 degrees C). Grease a 12-cup muffin tin or line cups with paper liners.

Step 4
Stir flour, baking powder, baking soda, salt, cinnamon, and nutmeg together in a bowl. Set aside.

Step 5
Add cooled browned butter, maple syrup, and vanilla to the soaked oats. Whisk until combined. Add in egg and mix until thoroughly combined. Mix in 1/2 of the flour mixture and stir until just combined. Mix in remaining flour mixture, stirring until just combined. Fold in raisins and walnuts.

Step 6
Spoon batter into the prepared muffin cups, filling each 3/4 full.

Step 7
Bake in the preheated oven until tops spring back when lightly pressed, 15 to 18 minutes. Cool in the tin for 5 minutes. Transfer to a wire rack to cool completely.