>>21675969
After you rice them you immediate mix them with hot diary (Chef JP uses milk in the demonstration, but scaled heavy cream is also good) to raise the temperature back up and keep them on a low-fire while you sieve them.
Chef JP has a stickied comment under his video addressing the same question as well:
>They do indeed get a bit colder and need to be kept in a warm space, like a warm oven. At home the best thing you can do is make them in advance WITHOUT BUTTER, cover them with a plastic wrap and reheat them in the microwave (do not worry about the wrap it will NOT melt in the microwave) and only add lots of room temp butter a few seconds before you serve them.
You can either reheat them in the microwave or a low oven until they reach ~155-160*F then fold in your room temp butter to emulsify.