Extra Thick Double Cream is Double Cream that has been homogenized to produce the extra thickness that makes it spoonable right from the container as a topping for desserts and fruit. For this reason, it’s sometimes referred to as a “spooning cream.”
It won’t whip successfully, but the idea behind its being made extra thick is that it’s ready to go as a solid topping without your needing to whip it.
At Christmas, you can buy specially flavoured ones such as Cognac, Cointreau, etc.
Brits will use an Extra Thick Double Cream as a topping where North Americans would use ice cream or whipped cream.
It is also useful as a cake filling.