Preparing clotted cream is not difficult, but it does take time. Also one needs to have a source for cream that is not ultra-pasteurized or homogenized. It must be pasteurized, however.
This starts with 2 quarts of manufacturer’s cream.
After one hour over very low heat it looks like this:


After 4 1/2 hours it looks like this
And it has another 4 hours to go.


After 8 hours over very low heat and 4 hours of setting, this is the final result:

Lovely clotted cream, no additives, no preservatives.
a close-up view of the thick cream which will become firmer with chilling.

Now it’s time to bake some scones!
The remaining cream has been mixed with non-homogenized milk, the “cream-top” stuff, and will become cheese or yogurt.
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Or – You can use one of the mild or “sweet” yogurt cultures (available from New England Cheesemaking Supply Company.
You must use heavy cream and incubate for 18-24 hours to get the perfect consistency and flavor. This can also substitute for Creme Fraiche.
Here is a link to another blog that has instructions for preparing clotted cream in the oven.
Cupcake Project Blog: Recipe for Clotted Cream
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I first posted this “recipe” and photos on eGullet in November 2007.
Preparing Clotted Cream
There are some follow up comments that might be helpful to my readers.