Some of the VLCDs use things like Mix a Mousse to make the shakes into a mousse so I thought I'd give it a whirl with a Slim and Save shake. If you can get hold of Mix A Mousse from the Cambridge diet then that's the simplest way (but it's quite expensive) or you can use powdered gelatine.
I had some Mix A Mousse left over from when I did a VLCD before so I tried yesterday with a strawberry shake and it came out fine (but I did end up with a couple of small lumps).
Today I tried with normal gelatine powder from the supermarket. I used half a sachet of gelatine and disolved the gelatine in a measuring jug in a little boiling water (about 50ml). I did whizz it in the microwave for 10 seconds to disolve the last bit as there was still a little that wasn't disolved (but you shouldn't allow it to boil). Gelatine liquid was then put into the fridge to cool.
Once cool I topped it up with cold water to 150ml and added the liquid to a shaker and tipped in the shake powder. Shake until blended as per a normal shake (but it's thicker) and then add to a bowl. I then added a little more water to the shaker and shook to ensure that I got every last bit of the shake stirred it into the bowl with the rest and put into the fridge to set. I'm not sure how long it took to set as I got distracted but it's supposed to take 10 - 15 minutes. It was quite nice (I used banana) and quite firm. It's not to everyone's taste but it made a bit of a change.
Given how firm it was I would think that you might be able to get away with a bit less gelatine, or more liquid but you'd need to play around with that to suit your own personal taste.
Dr Oetker Gelatine powder is 69p in Tesco for 6 sachets (ie 12 mousses!) but make sure that you get the powdered gelatine, not the leaf or the sheets. It's not for veggies though as it's 100% meat protein. There is a vegetarian gelatine but I'd suggest that is not good as it's 90% carbohydrate. Cambridge diet say that you can have 1 shake per day made into a mousse so I guess we can probably do the same with no problems.
There are also threads in Minimins about making a trifle from a jelly made of water with added water flavouring (if you use those) and gelatine as the base and the mousse on top. No trifle sponges though!