Mince shallots and garlic very fine. In a large skillet or saucepan, add butter and shallot and cook over low heat until shallots are transparent, about 5 minutes. Season with a pinch of salt.
Add garlic and cook for 30 seconds. Then add flour and stir to distribute flour. Turn heat up to medium-low and cook for a minute or two just to cook out flour taste.
Slowly stir in warmed cream in a slow drizzle. Stir or whisk constantly so lumps don’t form.
Bring cream mixture to a very slight simmer and cook until it thickens slightly. If you move a spatula through the sauce it should leave a nice streak.
When sauce is the consistency of a gravy, season with fresh thyme and a pinch of salt and pepper.
Let sauce cool to room temperature before using or you can make in advance and chill. Don’t worry if the sauce solidifies if you chill it. You can still spread it on the pizza and it will turn back into a sauce in the oven as the pizza cooks.