Line the bottom and sides of a 20cm x 20cm square baking tin with greaseproof / parchment paper.
Put the raisins in a glass bowl and pour over enough boiling water just to cover them. Wait 10 minutes until the raisins have plumped up. Drain the raisins but keep the raisin water.
Add the raisins, peanuts, cocoa powder, chocolate chips and vanilla into a food processor. Process until the mixture is well combined and sticking together. If the mixture is not sticking together add a little of the reserved raisin water and process again.
Put the combined sticky mixture into the lined baking tin and flatten it out all over by pressing down with the tips of your fingers making sure the bottom of the tin is evenly lined.
Place the baking tin into the fridge overnight.
In the morning, remove from the fridge, lift out the hardened slab using the greaseproof paper onto a cutting board, and cut into 16 squares.
Store in a fridge in an airtight container to keep as fresh as possible until time to eat.