Roll out the pastry on a lightly floured surface and use to line a 23cm tart tin – keep any leftover pastry in case you need to fill any cracks after blind-baking. Prick the base with a fork and chill for 30 mins or until firm.
Heat oven to 190C/170C fan/gas 5. Line the pastry case with baking parchment, fill with baking beans and bake for 15-20 mins until the sides are set. Remove the beans and parchment and return to the oven for 5-10 mins until the base is set and the pastry is golden. Leave to cool.
Increase oven to 200C/190C fan/gas 6. Beat the butter and sugar together with an electric whisk until light and fluffy. Keep the beaters going and pour in both of the syrups. Gradually add the eggs, 1?4 tsp salt and the vanilla, then whisk until combined. Stir through the nuts and pour into the tart case. Bake for 10 mins. Turn heat down to 160C/140C fan/gas 3 and continue baking for 30-35 mins – the pie should be golden brown but the filling should wobble a little in the centre when shaken. Leave to cool in the tin. You’ll probably need to run a knife down the side of the tin to release the pie. Serve with whipped cream.