how to whip UHT cream?
UHT and ultra-pasteurized creams can be whipped, but it can be more difficult than pasteurized cream. From  The Cultured Cook :


  The key to lush whipped cream is choosing lush cream to begin with. Ideally, you want cream from grass-fed cows — it has a richer, fuller taste and a lighter, fluffier texture — and cream that has not been UHT pasteurized. UHT means “ultra-high temperature,” which in turn means that the cream will be difficult to whip since it’s been thoroughly cooked and in the process has lost a great deal of its natural thickness and ability to hold that thickness when whipped. (Whipping simply incorporates air into the cream. The fat in the cream stiffens around the air pockets and holds itself up to create the fluff effect. Cold fat is stiffer than room-temp fat, which is why using chilled equipment and chilled cream is so important.) Take a look at the ingredient list on UHT whipping cream — you’ll see that it’s been thickened with carrageenan, gums, and other stabilizers to recreate the thick texture the cream has lost through having been overheated. Not exactly an ideal scenario.


Some pointers mentioned in comments above that may make a difference in how much success you have when whipping any cream, but especially UHT cream:


You need a fat content of at least 30%.
The cream should be cold. Some people also refrigerate their bowl and utensils also.
You can purchase stabilizers to add to UHT cream to help ensure proper results. Cream of tartar is one option.


Bonus #1 - Issues can occur with other heat treated products. E.g., pasteurized egg whites are more difficult to whip into peaks. While I have read that it can be done, I have never succeeded. I have also been told that cream of tartar (a stabilizer) can make it work.

Bonus #2 - The difference between UHT and ultra-pasteurization is not the process, but the container. They both use ultra high temperature pasteurization.


With UHT milk products, the sterile products are put into sterilized (aseptic) containers and hermetically sealed using a heat process. Now they are shelf stable and have a shelf life of 6 to 9 months (until opened).


Ultra-pasteurized milk products go through the same process but are put into regular milk containers (like pasteurized milk products) and must be kept refrigerated. It has an extended shelf life and should keep 2 to 4 weeks longer than pasteurized milk products (until opened).