Adding double cream to a curry can help cool it down, as the creaminess and fat content can help balance out the spiciness. However, it's important to note that adding cream can also thicken the sauce and make it richer, so it's best to add it gradually and taste the curry as you go to ensure that it doesn't become too heavy. Additionally, if you're looking to cool down a curry but don't want to add cream, you can also serve it with a side of plain yogurt or raita, which can help balance out the spiciness and add a refreshing touch to the dish.