Chef John's Clotted Cream
This works best with good quality cream, preferably from grass-fed cows with a fat content of between 36% to 40%. Avoid anything that says "ultra-pasteurized," since it's been heat-treated, and you'll not get the same results.
Most modern ovens go down as low as 175-180 degrees F (80 degrees C), which is ideal for this technique. 200 degrees F (95 degrees C) will work, but maybe check after 10 hours, and see how things look.