Pre-heat the oven to 200C/400F/Gas 6.
If using a shop bought sweet crust pastry case, use one that is 23cm/9in diameter and 4cm/1½in deep. If using your own pastry, roll it out and use it to line a 23cm/9in pie plate (not loose bottomed). Bake the pastry case blind for 20 minutes.
To make the filling, place the pumpkin chunks on a baking tray, cover with foil and roast until tender. This will take about 20-30 minutes, depending on your pumpkin. Press the cooked pumpkin in a coarse sieve and to extract any excess water. Set aside to cool before blending in a food processor, or mashing by hand to a pureé.
Lightly whisk the eggs and extra yolk together in a large bowl.
Place the sugar, spices and the cream in a pan, bring to simmering point, giving it a whisk to mix everything together. Then pour it over the eggs and whisk it again briefly. Now add the pumpkin pureé, still whisking to combine everything thoroughly.
Reduce the oven temperature to 180C/350F/Gas 4. Pour the filling into your pastry case and bake for 35-40 minutes, by which time it will puff up round the edges but still feel slightly wobbly in the centre.
Remove the pie from the oven and place the tin on a wire cooling rack. Serve warm or chilled (stored loosely covered in foil in the fridge) with some chilled créme fraïche or whipped cream.