2 ounces white baking chocolate (with cocoa butter), melted and cooled slightly
2 ounces milk chocolate, melted and cooled slightly
3 tablespoons hazelnuts (filberts), toasted and chopped (see Tip)
1 ounce dark chocolate or bittersweet chocolate (optional)
½ teaspoon shortening (optional)
Line an 8x4x2- or 9x5x3-inch loaf pan with heavy foil, extending foil up over the edges of the pan; set pan aside. In a medium bowl, beat one-third of the cream cheese with an electric mixer on medium speed for 30 seconds. Beat in the 2 ounces melted dark chocolate until smooth. Fold in about one-third of the dessert topping. Spread mixture evenly in the prepared pan. Cover and freeze about 30 minutes or just until firm.
Meanwhile, in another medium bowl, beat half of the remaining cream cheese with an electric mixer on medium speed for 30 seconds. Beat in melted white chocolate until smooth. Fold in half of the remaining dessert topping. Spread white chocolate mixture evenly over frozen dark chocolate layer in pan. Cover and freeze about 30 minutes or just until firm.
Meanwhile, place remaining cream cheese in another medium bowl. Beat with an electric mixer on medium speed for 30 seconds. Beat in melted milk chocolate until smooth. Fold in the remaining dessert topping. Spread milk chocolate mixture evenly over the frozen white chocolate layer in pan. Sprinkle with hazelnuts. Cover and freeze for 2 to 24 hours.
To serve, use the edges of the foil to lift the mousse out of the pan. If necessary, let stand at room temperature about 20 minutes to soften slightly. Cut loaf crosswise into 10 pie-shape wedges. If desired, melt together dark chocolate and shortening; drizzle over mousse slices.
Tip: To toast hazelnuts, preheat oven to 350°F. Spread hazelnuts in a single layer in a shallow baking pan. Bake for 8 to 10 minutes or until portions of the nuts visible through skin appear lightly browned, stirring once or twice to prevent burning. Cool nuts slightly. Pour out onto a clean kitchen towel. Fold towel over nuts; rub gently with towel to remove skins.