Preparation:
Garnish if desired: 1/4 cup chopped toasted skinned hazelnuts
Chop chocolates into small pieces and in a double boiler or a metal bowl set over a saucepan of barely simmering water melt chocolates with hazelnut butter, stirring until smooth. Remove top of double boiler or bowl from heat.
Split vanilla bean lengthwise and scrape seeds into a 3-quart heavy saucepan. Add pod, milk, and cream and bring mixture to a simmer over moderate heat. Remove pan from heat.
In a large bowl with an electric mixer beat together yolks and sugar until thick and pale. Add hot cream mixture to egg mixture in a slow stream, whisking, and pour into pan. Cook custard over moderately low heat, stirring constantly, until a thermometer registers 170ΓΈ F. (do not let custard boil or it will curdle).
Pour custard through a sieve into a clean bowl and stir in chocolate mixture until combined well. Chill custard, its surface covered with plastic wrap, until cold, at least 1 hour, and up to 1 day.
Freeze custard in an ice-cream maker. Transfer ice cream to an airtight container and put in freezer to harden. Ice cream may be made 1 week ahead.
Serve ice cream sprinkled with hazelnuts.
Makes 1 quart. |