White Chocolate Mousse With Frangelico
["8 oz. white chocolate, broken into small pieces", "1/2 c. (1 stick) unsalted butter", "6 eggs, separated (at room temperature)", "1 c. sifted confectioners sugar", "1/2 c. Frangelico liqueur", "2 c. whipping cream, cold", "pinch of cream of tartar", "unsweetened cocoa powder or grated dark chocolate (for garnish)"]
["Melt the white chocolate and butter in a small saucepan, stirring constantly.", "Set aside. Beat egg yolks, sugar and liqueur until the mixture forms a slowly dissolving ribbon when the beaters are lifted.", "Pour the mixture into the top of a double boiler and cook, whisking constantly, over simmering water until very thick, about 3 minutes.", "Remover to a large mixing bowl. Whisk in the white chocolate mixture and stir until smooth and cool.", "Beat the cream until the peaks are stiff."]
["white chocolate", "butter", "eggs", "confectioners sugar", "Frangelico liqueur", "whipping cream", "cream of tartar", "cocoa"]