Heat oven to 350°F Spray bottom and sides of 2 (9X2-inch) round cake pans with nonstick cooking spray. Line bottoms with parchment paper; spray parchment. Flour bottom and sides of pan.
In medium bowl, stir together flour, baking powder and salt. In medium saucepan, combine milk, 1/2 cup butter and 2 oz. white chocolate; heat over medium-low heat until butter and chocolate are melted and mixture is smooth and hot, stirring frequently. (Mixture should be about 150°F.).
Meanwhile, in large bowl, beat eggs and sugar at medium speed 3 to 4 minutes or until thick, fluffy and lightened in color. Beat in 1 teaspoon vanilla and 2 teaspoons orange peel. At low speed, beat in flour mixture until blended. Slowly beat in hot milk mixture until smooth. Pour evenly into pans. Bake 30 to 35 minutes or until toothpick insterted comes out clean. Cool in pans on wire rack 20 minutes. Run knife around edges of pans to loosen cakes. Invert onto wire rack; remove parchment. Cool completely.
To make frosting, fill medium saucepan one-fourth full with water; bring to a simmer over medium heat. Remove from heat. Place 6 oz. white chocolate in medium heatproof bowl; place over saucepan, making sure bowl does not touch water. Stir frequently until chocolate is smooth and melted. Let cool slightly. In large bowl, beat cream cheese and 1/2 cup butter at medium speed until blended and smooth. Beat in melted white chocolate until blended. Beat in 2 teaspoons vanilla and 1 teaspoon orange peel. At low speed, beat in 4 cups of the powdered sugar, adding additional powdered sugar if needed for spreadable consistency. Beat until blended and smooth.
Place 1 cake layer on serving platter or cardboard round; spread top with 1 cup of the frosting. Top with second layer. Spread cake sides with thin layer of frosting (A crumb coat). Coat sides with another smooth layer of frosting. Spread remaining frosting over top. Spoon white chocolate curls over top of cake, mounding slightly towards center.
(Cake can be made up to 2 days ahead. Cover and refrigerate. Bring to room temperature before serving.