Mash bananas with egg yolks and let sit 30 minutes
Melt butter in a small saucepan over medium-high, whisking constantly for 3-5 minutes until golden and nutty, then whisk 30-45 seconds more until chestnut colored. Pour into a heat-safe container and cool
In a large bowl, beat browned butter and brown sugar until combined. Add whole eggs, mashed banana mixture, yogurt, and vanilla. Whisk smooth
In another bowl, whisk flour, baking soda, baking powder, salt, and cinnamon. Gently fold into the wet mix until just a few dry streaks remain. Fold in walnuts
Cover and rest the batter 45-60 minutes at room temperature, or overnight in the fridge
Preheat oven to 425°F. Line or grease 12 jumbo muffin cups. Fill each ⅘ of the way. Top with extra walnuts, banana slices, and/or turbinado sugar. Bake at 425°F for 6 minutes, then drop to 350°F and bake 18-20 more minutes, or until a toothpick pulls out with a few crumbs
Rest in the tin 5-10 minutes, then transfer to a cooling rack
