The top of this pie has a chewy-biscuit texture from the brown
sugar, while fennel seeds add a lovely note of spice to the pastry.
Be careful not to overcook the rhubarb to begin with or it will
fall apart as the pie bakes.
2large bunches rhubarb, trimmed120 gmraw sugarJuice and finely grated rind of 1 orange1 tsp cornflour, mixed with 2 tsp waterVanilla ice-cream, to serveBrown sugar and fennel pastry1½ tspfennel seeds½ tspblack peppercorns170 gmsoftened butter195 gm brown sugar255 gmplain flour, sieved1½eggs, lightly whisked
For brown sugar and fennel pastry, dry-roast fennel seeds and peppercorns in a small frying pan over low heat until fragrant (3-5 minutes). Beat butter in an electric mixer fitted with a paddle attachment until pale (4-6 minutes), mix in sugar and ¾ tsp fine sea salt, then add flour and toasted spices, and mix to combine. Add egg and mix to combine. Turn out pastry, pat into a disc, wrap in plastic wrap and refrigerate until firm (1 hour). Roll pastry between sheets of baking paper or Go-Between (plastic sheeting) to fit the top of a 23cm-diameter pie dish and refrigerate until required.
Preheat oven to 190C. Wash rhubarb well and peel off the tough outer fibres, leaving as much colourful peel as possible (the larger the stems the more vigilant you need to be). Chop rhubarb into 5cm pieces, then transfer to a saucepan along with sugar, and orange juice and rind, and cook over medium heat until rhubarb starts to seep liquid and just softens on the outside (2-3 minutes). Transfer fruit to a 23cm-diameter pie dish with a slotted spoon, whisk cornflour slurry into liquid and bring to the boil, whisking until a syrup forms (2-4 minutes). Pour onto rhubarb and cool briefly.
Place pastry on top, trim edges and bake, turning once or twice, until filling is bubbling and pastry is golden (25-35 minutes). Serve warm with ice-cream.