Hmmm I seem to recall someone making clotted cream a few years back ...
Here is a method from a book published in 1920
Devonshire Cream. Clotted cream is chiefly made in
Devon, Somerset, and Cornwall. It is, however, possible
to make it in any part of the country where milk
of good quality is available. The warm milk is strained
into shallow pans 6 to 8 in. deep and allowed to stand
undisturbed for 12 or 24 hours, the length of time
varying with the time of year.
The pans are now removed to a stove and the milk
heated very gradually to a temperature of 170 to 190
Fahrenheit. This should be done very slowly, or the
proper flavour is not obtained about 20 to 30
minutes is the minimum time which should be
taken.
The pans are then removed to the dairy and allowed
to cool, and in summer they are often placed in cold
water. The cream is skimmed off after about 12 hours,
using a perforated skimmer. Clotted cream may be
churned, but in this case the scald is not so high, 170
Fahrenheit being the maximum.
The old-fashioned method of churning clotted cream
was to place it in a tub and stir or beat with the hand
till butter is produced. Butter made from clotted cream
requires thorough washing to remove the butter-milk
or the keeping properties will be poor.
Cream Ripening. The management of the cream
from the time it leaves the separator until it is churned
is a matter of the greatest importance. The flavour,
the texture, and the keeping properties of the butter
are influenced by the conditions under which the cream
has been kept. Cream may be churned either in a
sweet or in a ripened condition.
In some districts there is a good demand for butter
made from sweet cream. This butter is paler in colour
than that made from ripened cream, and has a mild
creamy flavour. It is usually considered to have poor
keeping qualities, but if carefully made and thoroughly
washed to remove the buttermilk it will be found to
keep in good condition for a reasonable time. The loss
of fat is greater in churning sweet or unripened cream,
though this loss need not be more than 1 per cent, if
the churning temperature is properly regulated.
If the cream is to be churned sweet, it should be
thoroughly cooled on leaving the separator and kept at
a fairly low temperature for several hours before being
churned. This gives a firmer butter than if the cream
were merely cooled just before churning. The usual
practice is to ripen the cream before churning.