St. Patrick’s Day Ombre Cake

Name: St. Patrick’s Day Ombre Cake
Prep time: 40 min
Cook time: 22 min
Total time: 1 h 2 min
Cuisine: American
Ingredients: White Cake; 3/4 cup unsalted butter, softened to room temperature; 3/4 cup vegetable shortening; 3 cups granulated sugar; 12 egg whites, room temperature; 1 1/2 tablespoon vanilla extract; 4 1/2 cups all-purpose flour; 1 1/2 tablespoon baking powder; 1/2 teaspoon salt; 1 ½ cup milk; Green food coloring; 2 cup unsalted butter, room temperature; 8 cups powdered sugar, sifted; 4 teaspoons vanilla; 1/2 cup milk