Start by browning the butter. Add butter to a small saucepan over medium heat and melt. Once melted stir constantly. Butter will be really bubbly and foamy. Once most of the foam subsides and you can see the butter has turned medium-dark brown, remove from heat and pour into a heat safe bowl. Let cool.
Preheat oven to 425 ℉. Line a jumbo (6 cup) muffin pan or regular sized (12 cup) muffin pan with muffin liners. Set aside. In a medium size bowl mix together the browned butter, sugars and vanilla until combined. Whisk in the eggs, sour cream and buttermilk until smooth. Set aside.
In a large bowl, whisk together the flour, baking powder and baking soda. Create a well in the center. Add the wet mixture and chocolate chips. Mix gently just until combined, scraping down the sides of the bowl once or twice to make sure all the flour is incorporated. Let the batter rest for 15 minutes.
Use an ice cream scoop or measuring cup to fill the muffin cups all the way to the top. Top with more mini chips if desired and bake for 7 minutes. Reduce oven temperature to 350 ℉. Bake for an additional 15-20 minutes or until a toothpick inserted in the center comes out clean. Let the muffins cool a bit in the pan before removing and enjoying!