In a small, heavy saucepan, bring the cream to a bare simmer over low heat. Place the chocolate pieces in a medium bowl. Remove the cream from the heat and pour over the chocolate. Let mixture stand for 2 minutes, then whisk until the chocolate is melted. Add the vanilla extract and banana liqueur and continue whisking until the sauce is smooth and slightly thickened. Serve warm, or let cool to room temperature.
Yield: 1 1/2 cups