Sushi Cake

Name: Sushi Cake
Ingredients: Cooking spray; 1 15- to 16-ounce box yellow cake mix (plus required ingredients); 1 16-ounce tub white frosting; 1 cup bright white candy melts; 3/4 cup puffed rice cereal; 4 to 5 pieces dried mango or papaya; 1/2 green apple, cut into small pieces; Juice of 1/2 lemon; 1 10-ounce bag mini marshmallows; 1 1-pound box confectioners' sugar; 1 1/4 cups dark cocoa powder, plus more for dusting; 4 tablespoons unsalted butter, at room temperature; Green food coloring; 4 to 5 pink Starburst candies