For a richer flavor, use brown butter instead of regular butter to caramelize the onions. Add a pinch of red pepper flakes to the sauce for a touch of heat. The reserved roasted garlic oil is excellent for drizzling over roasted vegetables or using as a base for salad dressings. If you don't have fresh thyme, you can use 1/2 teaspoon of dried thyme. To make ahead: The caramelized onions can be made up to 3 days in advance and stored in the refrigerator. Reheat before adding the cream and cheese.