In a small saucepan heat cream and Grand Marnier to a boil. Place chocolate in a fondue pot or top of a double broiler. Pour cream mixture over chocolate and heat over low heat, stirring constantly, until smooth. Arrange fruits on a pretty platter, garnished with mint sprigs. Place pot of chocolate over a small candle or alcohol burner and adjust so heat is very low. Use long forks to dip fruits and sweets into chocolate.