To make the puree, put cubed pumpkin pieces in a pot. Add sugar and just enough water to cover the pumpkin. Cover pot and simmer mixture until pumpkin turns tender. Drain well, then blend into puree. Sieve to remove impurities.
To prepare the sweet pastry, put flour and salt into a mixing bowl. Rub in chilled butter until the mixture resembles fine breadcrumbs. Add sugar; mix. Add egg and mix until a dough is formed. (If dough is too dry and crumbly, sprinkle a little water until mixture holds together.)
Put dough on a lightly-floured tabletop and knead till smooth. Shape dough into a ball. Wrap with cling film. Chill in refrigerator for 20 to 30 minutes.
Grease a 20cm loose-bottomed flan tin with corn oil. Roll out pastry to about 2mm or 3mm thickness and line the flan tin with it. Prick dough with a fork and chill for 30 minutes.
Preheat oven to 190ºC. Bake blind for 10 to 15 minutes until pastry turns firm. Remove beans and paper and bake for a further five to 10 minutes. Leave to cool.
To prepare filling, put pumpkin puree, eggs, sugar and the rest of the ingredients into a mixing bowl. Whisk until smooth and well-blended. Pour filling into the prepared pastry case and bake in a preheated oven at 160ºC for 25 to 30 minutes or till filling is firm to the touch. Leave pie to cool in the tin. Serve warm or chilled.