For the base, pulse the ginger biscuits in a food processor to small chunks. Add the remaining ingredients and lightly pulse until incorporated.
Grease and line a brownie tin with baking parchment and pour in the mixture. Spread it around the tray and press into the edges until even and smooth, then place in the fridge to set.
Place all of the ingredients for the caramel in a high-speed blender and blend until you have a thick, smooth paste.
Remove the tray from the fridge and spread over your layer of caramel, using a palette knife dipped in hot water to smooth the top, returning the tray to the fridge once more.
Melt the chocolate by placing it in a heatproof bowl set over a pan of simmering water (do not allow the base of the bowl to touch the water). Pour the melted chocolate over the caramel and return the tray to the fridge to set for 1-2 hours. Once set, cut into neat slices or chunks to serve or gift.