For the base: Line the base of an 8″ high sided, loose-bottomed or spring form tin with baking paper. Blitz the digestives in a food processor until fine crumbs. Then add the melted butter and blitz again until it starts to hold together. Tip this into your lined tin, and using a spoon (or your hands), compact the base down. Then chill in the fridge for 20 minutes.
For the cheesecake: Using an electric hand-whisk beat the cream cheese and icing sugar together in a large bowl. Then mix in the peanut butter and beat again till combined. Finally, beat in the double cream until the mixture thickens. Pour this on top of the chilled base and level out. Then cover and leave in the fridge overnight or for at least 4 hours.
For the salted caramel sauce: Place the sugar, golden syrup and water in a heavy-bottomed pan and stir to combine. Place over a high heat, occasionally swirling the pan (try not to stir), until it turns a medium gold amber colour – this will take about 10 minutes. Then remove the pan from the heat and slowly and carefully whisk in the cream, the mixture will bubble up so be careful and keep stirring. Next add the butter, whilst continuing to stir until melted. Then add the salt and vanilla to combine, Pour into a heat-safe container (a pyrex bowl, jug or a jam jar will do) and set aside to cool and thicken (will take about 11/2 hours).
To decorate: Once the cheesecake has set and the caramel has thickened, place the caramel into a piping bag. Pipe lines across the cheesecake, then scatter the chocolate covered peanuts around the edge.
Cheesecake is best served straight from the fridge and can be kept in an air-tight container in the fridge for 4-5 days.