Preheat the oven to 150C. Carve the pumpkin into even fist-sized chunks and roast in the oven for 3 - 4 hours, until a knife sinks into it with no resistance. Cover with foil and leave to cool.
To make the pastry, whisk the egg yolks with icing sugar until frothy. Rub the butter into the flour, lemon and salt until it resembles breadcrumbs. Combine the yolk mix with this until you get a smooth pastry and then wrap in the fridge to rest for 30 mins.
Roll out the pastry to 3mm thick. Press into a pie dish, prick all over and blind bake for 30 mins until browned.
When the pumpkin is cool peel away from the skin and pulse in a food processor. When smooth whisk with the remaining filling ingredients and pour into the pastry case. Bake for 20 mins or until the centre of the pie reaches 70C when checked with a temperature probe. Leave to cool and serve with whipped cream.