Pour the cream into a heavy-bottomed oven-safe pot.
Cover the pot and put it in the oven on 180 F for at least 8 hours.
You’ll know it’s done because there will be a thick yellowish skin above the cream; this is the cream.
Let the pot cool at room temperature, then put it in the refrigerator for another 8 hours.
Skim and reserve the clotted cream from the top of the pot.