Preheat oven to 350. Grease and flour two round cake pans; set aside. In medium bowl combine flour, baking powder, 1/2 tsp salt and nutmeg; set aside.
In a large mixing bowl beat butter on medium high speed for 30 seconds. Gradually add granulated sugar; beat until combined. Beat two minutes more. Add eggs, one at a time, beating well after each addition. Alternately add flour mixture and 3/4 cup of the mango juice; beat on low after each addition just until combined. Stir in shredded carrot. Pour into prepared pan.
Bake 25 to 30 minutes or until golden and wooden pick inserted near center comes out clean. Cool in pans on wire rack 10 minutes. Remove from pans; cool completely. Place remaining 1/2 cup mango juice blend in a small saucepan; bring to boiling. Boil gently until reduced to about a 1/4 cup; cool completely.
Cream cheese frosting: In a large bowl beat together one 8 oz package of cream cheese and 1/4 cup butter until smooth. Beat in 1 tsp of vanilla and gradually add 4 cups of powdered sugar.
Frost cake tops and drizzle with reduced mango juice.
Carrot ribbons: Use vegetable peeler to make long ribbons the length of carrot. Place in ice water for 30 minutes. Top frosting with carrot ribbons.