03Serve bananas like a banana split with ice cream and chocolate sauce.
04In a 2 1/2- to 3-quart heavy saucepan combine cream and milk. Scrape seeds from vanilla bean into cream mixture, dropping in bean. Add zest and bring mixture just to boil.
05In a large metal bowl whisk together brown sugar and yolks until combined well. Add hot cream mixture to yolk mixture in a slow stream, whisking, and return custard to pan. Cook custard over moderately low heat, whisking constantly, until thickened and coats back of a wooden spoon, about 3 minutes. (Do not let custard boil or it will curdle.)
06Pour custard through a very fine sieve into cleaned metal bowl and cool slightly. Stir in rum and chill, covered, until cold. Freeze custard in an ice-cream maker. Makes about 1 1/2 quarts.
07In a heavy saucepan heat chocolate and half-and-half over low heat, stirring frequently, until chocolate is melted. (The sauce will have a very thin consistency, like that of hot chocolate.) Serve sauce warm. Makes about 1 cup.