Banana Muffins with Mascarpone Cream Frosting

Name: Banana Muffins with Mascarpone Cream Frosting
Ingredients: 3 cups all-purpose flour; 1 teaspoon baking soda; 1 teaspoon salt; 1/2 teaspoon baking powder; 1/2 teaspoon ground cinnamon; 1/2 teaspoon ground nutmeg; 2 cups sugar; 1 cup vegetable oil; 3 large eggs; 1 tablespoon vanilla extract; 4 ripe bananas, peeled and coarsely mashed; 3 ounces cream cheese, room temperature; 6 tablespoons (3/4 stick) unsalted butter, room temperature; 1/3 cup mascarpone cheese, room temperature; 3 tablespoons honey; 1/2 cup chopped walnuts, toasted