Chocolate Zucchini Cupcakes

Step 1
Preheat the oven to 350 degrees F (175 degrees C). Grease two 12-cup muffin tins or line with paper liners.

Step 2
Beat brown sugar and eggs in a large bowl with an electric mixer until thick and pale, about 10 minutes. Blend in oil and melted chocolate.

Step 3
Stir flour, baking powder, baking soda, and salt together in a separate bowl; stir flour mixture into egg mixture until just blended. Stir in zucchini and 1/2 cup walnuts. Using an ice cream scoop, spoon batter into the prepared muffin cups, filling each 2/3 full.

Step 4
Bake in the preheated oven until a toothpick inserted in the center comes out clean, about 20 minutes. Remove from the oven and cool in the pans for 10 minutes, then transfer to a wire rack to cool completely, 20 to 30 more minutes.

Step 5
Spread frosting over cooled cupcakes and garnish with remaining walnuts.