Strain the stock and put in a sealed container. It should stay fresh for up to three days.把高汤滤出来放在一个密封的容器里，这应该可以保鲜三天。Combine the stock, whole onion and peppercorns in a pan and bring to a simmer.将高汤、一整头洋葱和胡椒粒一起放入锅里用文火慢煮。Make the sauce by boiling the cream and stock together in a pan.把奶油和高汤一起放在平底锅里熬煮来制作调味料。