Can I add normal milk or cream with a 30% fat content to clotted cream with a 58% fat content to make whipping cream? can clotted cream be whipped on its own? I want to decorate a cake.
I have never actually tried it, but clotted cream is made by gently heating heavy whipping cream for 12 hours or so, which causes the fat to separate and coagulate on the top. I have tried to infuse heavy whipping cream with tea flavors in the past by gently heating it for a far shorter amount of time, resulting in no visible change to the cream's structure. Even after thoroughly re-chilling the cream, it did not whip up like normal heavy cream at all.
I did achieve some measure of success when I added some fresh heavy cream to my infused cream, but it still had a different consistency from whipped cream and lacked the normal stability I would have expected.
So to answer your question, you probably won't get exactly what you want. The fresh cream you add will likely whip, and the clotted cream is thick enough that you might not have the stability issues I had, but it definitely won't be a regular whipped cream.
I would be careful whipping it at all, however. Clotted cream was initially invented as another way to make butter, and trying to whip it will likely turn to butter more quickly than regular cream.