Heat oven to 325 degrees F. Coat two 8 x 2-inch straight-sided round cake pans with nonstick spray; line bottom of pan with waxed paper. Coat waxed paper with spray. Set aside until batter is ready.

Mix flour, baking powder and salt in a small bowl. Set aside.

With mixer on medium speed, beat butter and granulated sugar in bowl until light. Add egg whites, one at a time, beating well after each addition.

On low speed, beat in flour mixture alternately with buttermilk, beating after each addition. Stir in 2/3 cup of the mini chips. Divide batter evenly between prepared pans. Spread level.

Bake at 325 degrees F for 37 to 39 minutes, or until cakes spring back when pressed. Cool in pans on a rack for 15 minutes. Invert cakes; remove pans and paper. Turn right side up; cool completely.

Place remaining chips (1-1/3 cups) in a glass bowl. Microwave on HIGH 30 seconds and stir. Heat 45 seconds more; stir until smooth. Set aside. In large bowl, beat together confectioners' sugar and heavy cream until blended, 1 minute. Beat in half of the melted chocolate, then remainder. Beat 1 minute, until shiny, smooth and good spreading consistency, scraping down bowl halfway through.

Place one cake layer on a pedestal or platter. Spread with 2/3 cup frosting. Top with second cake layer. Spread side and top of cake with remaining frosting (if frosting becomes stiff, use warm spatula to spread). Garnish with chocolate curls.