AHi

My friend and I want to make a cake recipe So we want to make one with digestive biscuits as the base...and we know how to do this

As for the second layer we are thinking of mixing raffaello and melt galaxy chocolate and mix them together and pour them over the base BUT what should we do? Should we wait for the melted galaxy to cool and then mix? Should we add sugar? Should we add butter? Whipped cream? Would the raffaello and galaxy taste good together? AND after that for how long do we put it in the fridge? And will they stick together after taking them out of the fridge like a normal cake? Please please please help us!!

I have never heard of those ingredients, but why don't you just try the 3 flavors together and figure out if it is any good? I assume you mean a refrigerator cake, or icebox cake? I made a "cake" with graham crackers and strawberry cream cheese, and refrigerated it for a day, and it was solid, but I would never say it was like "normal" cake.

Those ingredients are common in the UK

AYes I mean a fridge cake!! How did it come out solid? Did you put anything like butter to make it stick together?? And what if I want to try a raffaello cake with out galaxy..or the opposite.. what should I put for it to come out like your cake?

Digestive biscuits are similar to graham crackers in the US. I would think to make the 'crust' with digestive biscuits, it would be similar to how you make a crust for a key lime pie in the US. You use butter and sugar with the crushed up crackers/biscuits to make the crust. the butter makes it all stick together..

http://en.wikipedia.org/wiki/Graham_cracker_crust

http://www.marthastewart.com/336402/graham-cracker-crust

(there are lots of recipes online, I'm just throwing the Martha Stewart one out there)

ps- I believe you can add chocolate to this type of crust too. I had a similar crust at the Four Seasons hotel in Prague last year (it was amazingly yummy)- as the crust in their cheesecake..it had chocolate and nuts and they had used digestive biscuits (just like a graham cracker crust). 

AThank you but I know how to make the base I just dont know what to put in the second layer! If I put the galaxy and raffaello alone and mix them and pour them over the base when I take it out of the fridge will it stick together and come out like a cheesecake or do I need to put butter?

oh sorry- I misunderstood your question.  I have no idea about that.

If your going to just melt chocolate its just going to set as chocolate if you want cheesecake you need creamed cheese
 

Im also confused about what your trying to make ?