Banana Nut Muffins With Brown Butter

Place a rack in middle of oven; preheat to 375°. Line cups of a standard 12-cup muffin pan with liners. Toast ½ cup chopped raw walnuts or pecans in a dry medium skillet over medium heat, tossing often, until golden brown, about 4 minutes. Transfer to a plate and let cool. Wipe out skillet with paper towels if needed.

Add ½ cup (1 stick) unsalted butter to same skillet and cook over medium until fragrant and milk solids turn a deep golden brown, about 4 minutes. Scrape butter into a large bowl and let cool 5 minutes.

Meanwhile, mash 3 large very ripe bananas on a cutting board or a large plate with a fork until mostly smooth.

Transfer bananas to bowl with butter and add 2 large eggs, ¾ cup (150 g) sugar, and 2 tsp. vanilla extract and whisk vigorously to incorporate. Add 1½ tsp. baking powder, ¼ tsp. baking soda, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt and mix to combine. Add 1 cup (125 g) all-purpose flour and ½ cup (63 g) whole wheat flour and mix until mostly incorporated. Add walnuts and ½ cup semisweet or bittersweet chocolate chips and mix just until evenly distributed and batter is completely combined.

Divide batter evenly among muffin cups (about 6 Tbsp. per cup; they should be almost completely full). Bake muffins until golden brown and a tester inserted into the center comes out clean, 18–24 minutes. Let muffins cool in pan slightly before serving. Do ahead: Muffins can be baked 3 months ahead. Freeze in resealable plastic bags. Thaw at room temperature overnight or in the microwave in 30-second bursts before serving.