To make the pastry, place the Walnuts in a food processor and blitz until finely chopped. Add the flour and butter and blitz until it resembles breadcrumbs. Add the egg yolk and up to 3 tbsp water and mix until it forms and soft dough. Wrap in clingfilm and chill for 30 minutes.

Preheat the oven to 200oC, gas mark 6.

Roll out the pastry on a lightly floured surface and use to line a 23cm fluted flan tin, prick the base with a fork and chill for 15 minutes.

Line the pastry case with scrunched up baking parchment and add baking beans and bake blind for 15 minutes, remove the beans and parchment and bake for a further 5 minutes. Allow to cool slightly.

Place the pumpkin in a food processor with the eggs, condensed milk and spices and blitz until smooth. Stir in the Walnuts and pour into the pastry case. Bake for 40-45 minutes until set and golden on top. Allow to cool before removing from the tin.

While the pie cools, mix the remaining 25g Walnuts, roughly chopped with the maple syrup and place on a small roasting tin, bake for 5 minutes until caramelised. Sprinkle over the pie to serve.