Combine the flour, sugar and salt in a large mixing bowl.
Add the butter and mix with your fingers until the mixture resembles coarse breadcrumbs.
Add the egg yolk and ice water and work that in with your hands. Check the consistency of the dough by squeezing a small amount together between thumb and forefingers: You want there to be just enough moisture to bind the dough so that it holds together without being too wet or sticky.
If it's still crumbly, add a little more ice water, 1 teaspoon at a time. When you get it to the right consistency, shape the dough into a disk and wrap it in plastic. Put it in the refrigerator and chill for at least 30 minutes.
Pre-heat the oven to 200°C/400°F.
In a mixing bowl, combine all the filling ingredients and mix well.
Roll out the pastry to fit into a suitable pastry dish and transfer to the dish. Cut off the excess.
Pour the Pumpkin mixture into the pastry case.
Place the pie in the oven. Bake for 10 minutes then turn the temperature down to 170°C/340°F and continue baking for 25-30 minutes. The edges of the pie should be just set with the middle still slightly jiggly.
Remove from the oven and allow to cool to room temperature. Place in the fridge and allow to chill completely.