Step 1

Heat oven to 190C/170C fan/gas Arrange the rhubarb pieces in a large roasting tin. Sprinkle over the sugar, orange zest and juice, grenadine and 150ml water. Cover with foil and bake for 25-30 mins until tender but not mushy. Scoop the rhubarb out of the tin into a sieve and reserve any juices, then leave to cool completely. Tip the rest of the liquid into a saucepan, along with the collected juices, and bring to the boil. Simmer for 15-20 mins or until reduced and syrupy. Leave to cool completely.

Step 2

To make the crumble topping, rub the butter into the flour until the mixture resembles fine crumbs, then stir through the demerara sugar, almonds and oats. Tip onto a baking tray lined with parchment and bake for 15 mins, shaking the tray every so often, until golden brown, then cool.

Step 3

Mix the Disaronno and orange juice together in a shallow dish. Dip each sponge into the liquid, leaving it for about 15 secs on each side, then arrange them in the base of a large trifle dish. Tip the mascarpone into a bowl and whisk until soft and smooth, then add the custard, a little at a time, and mix until combined. Arrange half the rhubarb pieces on top of the sponges, discarding the orange zest. Drizzle over 2 tbsp of the rhubarb syrup and top with half the custard mix. Follow with another layer of rhubarb, 1 tbsp of the syrup, and the remaining custard.

Step 4

Whip the cream and 2 tbsp sugar to soft peaks and dollop over the custard. Drizzle over the remaining rhubarb syrup, along with a scattering of the crumble topping. Tip any extra crumble into a bowl and pass around the table.