This is a sweet little game which, as with all Orchard Toys games, has been enjoyed by my children (5 and 7). It's made from good quality thick cardboard, so it's durable and barely shows the heavy use it's had.
The idea is that you have to fill your cauldron with ingredient cards, which have numbers on them as well as charmingly gory eyeballs/bones and so on. These are the answers to maths questions (mostly addition with some subtraction and basic multiplication), which are on separate cards. You pick a sum card, pick up an ingredient card with that number, and keep it if you're correct.
Of course this could easily be made at home with bits of card and a pen - but the thing which keeps my two going back to this game is the 'magic'. The question cards have the answers on the back - but they're only revealed by rubbing the heat sensitive ghost-shaped patch. Apparently, this never gets old! It also means it can be played independently since the children can check their own answers.
I've taken one star away from the rating just because it could get a little boring after a while, and so may not have the longevity of other Orchard Toys games. Once the sums were too easy, there would be no point playing, as whoever went first would always win if nobody made any errors. It would need a little jigging around to allow for different levels of skill between players (not that I'm speaking from bitter experience or anything...). That said, you can change the game so that you are given a number and have to find a sum to fit it, so that certainly increases the play value as it's a little more challenging.
In any case, it's been brilliant for my not-very-confident DD who, after filling her cauldron for the first time, proudly exclaimed "Mummy! I'm good at maths now!" - so although it may not remain a games cupboard staple for years, it's worth the low price if you want to provide some fun maths practice.