Rhubarb and pink grapefruit possets with poppy seed and pistachio shortbread

Method

1. Add the rhubarb and 300g of the sugar to a pan over a medium heat. Simmer for 10-15 minutes to make a compote (add a splash of water if the mixture starts to stick). Leave to cool, then divide among serving glasses or bowls. Keep in the fridge until needed.
2. Add the double cream, vanilla and remaining 200g sugar to a pan over a low-medium heat and stir until the sugar dissolves and the cream is steaming. Take off the heat. Save a quarter of the grapefruit zest to garnish, then add the rest to the cream along with all the juice. Transfer to a jug, then carefully pour the cream over the compote in the glasses/bowls. Sprinkle the reserved zest over  the top, then return to the fridge for at least 4 hours to set.
3. To make the shortbread, line a loaf tin with baking paper. Add the sugar, butter and flour to a food processor and pulse until it resembles fine breadcrumbs. Stir in the poppy seeds, then tip the mixture into the lined tin and push down until compact and flat. Sprinkle the pistachios over the top, push them gently into the mixture, then sprinkle with a little more sugar and chill for 30 minutes.
4. Meanwhile, heat the oven to 180ºC/160ºC fan/gas 4. Bake the shortbread for 25 minutes. Leave to cool completely, then turn out and slice into 8 equal fingers. Store in an airtight tub until needed. Serve the possets with the shortbread on the side.