Preheat the oven to 180°C / 350°F / Gas mark 4.
In a large saucepan, place the pumpkin or squash in and cover with water, and bring to the boil.
Cover with a lid and simmer for 15 minutes or until tender.
Drain and let cool.
Lightly sprinkle a clean surface with flour then roll out the pastry.
Use it to line a 22cm loose-bottomed tart tin.
Chill for 15 minutes.
Line the pastry with baking parchment and baking beans, then bake for 15 minutes.
Remove the beans and paper, and bake for a further 10 minutes until the base is biscuity.
Remove from the oven and allow to cool slightly.
Increase oven to 220°C / 425°F / Gas mark 7.
Mash the pumpkin or squash in a large bowl. In a separate bowl, combine the sugar, salt, nutmeg and half the cinnamon.
Mix in the beaten eggs, melted butter and milk, then add to the pumpkin purée and stir to combine.
Pour everything into the tart shell and bake for 10 minutes, then reduce the temperature back to 180°C / 350°F / Gas mark 4.
Continue to bake for 35-40 minutes until the filling has just set.
Leave to cool, then carefully remove the pie from the tin.
Dust over with cinnamon and serve with the chilled whipped cream.