Ingredients

Step by step

1. Line the base of a 20cm springform cake tin with a circle of baking paper, then add the custard creams to a food processor and blitz to fine crumbs. Tip into a bowl and add the melted butter. Mix well until it looks like damp sand and pack into the cake tin, pressing down with the back of a spoon to make a smooth base. Transfer to the fridge.
2. To make the filling, mix the mascarpone, custard and icing sugar with an electric hand whisk until well combined and starting to thicken. Add the cream and whisk until thickened again; it needs to be very thick, but be careful not to overwhisk the mixture when the double cream goes in. Fold through the conserve so it ripples through the mix.
3. Spoon onto the chilled base and smooth over the surface with a spatula. Cover with clingflim and chill for 2 hours.
4. Put the caster sugar and 200ml water in a wide pan, and bring to a gentle simmer, stirring until the sugar dissolves. Using a vegetable peeler, shave the rhubarb into long thin strips – you want the really pink outer layers so stop as soon as you hit the white middle, and keep that for a crumble. Gently lower 4 or 5 strips at a time into the sugar syrup for 45-60 seconds to soften. Remove with a draining spoon and leave to cool, then spread out on a baking paper-lined tray until completely cool. Repeat with the remaining strips.
5. Slide a knife around the edges to loosen the cheesecake then unclip and remove the tin, and transfer to a serving plate. Gently layer up the rhubarb strips, overlapping slightly, over the top of the custard, hanging over the edges of the cheesecake. Trim the rhubarb with a pair of scissors around the edge to get a neat finish. Chill again until ready to serve.
6. To serve, use a very sharp knife to gently cut through the lattice, or snip first with scissors, depending on how robust your rhubarb is. The cheesecake is quite mousse-like, so use a sharp knife dipped in hot water to slice it neatly.
7. Watch this...

   Rhubarb and custard cheesecake