Roast the Squash

1. Pre-heat the oven to 400 F. Cut the squash in half and place face side down on a parchment lined baking sheet. Bake until soft and tender, about 30-40 minutes. Remove from the oven and allow to cool. Scoop out the seeds then blend until smooth. Reserve 450 grams. If you have leftover puree store in the fridge for another use.  

Make the tart dough

1. Place the flour, sugar, salt, and butter into the bowl of a food processor. Process until the mixture forms a coarse meal, about 20 to 30 seconds. Add in the egg yolk and water. Pulse, until the mixture is just beginning to come together and form a soft ball around the base of the blade, 20 to 30 seconds more. Tip the dough out onto the work surface and use your hands to bring together into a uniform dough, forming into a disc and wrapping in plastic wrap. Refrigerate the dough for about one hour before using.
2. Arrange a rack in the center of the oven. Set a 23-cm (9-inch) fluted tart tin onto a baking sheet. Unwrap the dough onto a floured work surface. Begin to roll into a circle that’s about 1/4 inch thick. Carefully ease the pastry into the crevices of the tin, then run the pin over the top to trim the excess overhang. Transfer to the freezer for one hour. Preheat the oven to 350.  
3.  Place a piece of parchment paper into the prepared shell and fill with pie weights. Place on a baking sheet and bake for 15 minutes. Remove and let stand for 5 minutes then carefully remove the weights and parchment. Lightly brush over the egg white. Return to the oven and continue to bake for another 7 to 10 minutes, until the shell is light golden brown. Set aside while you prepare the filling.

Make the Filling 

1. In a large mixing bowl, whisk together the pumpkin purée, light brown sugar, and all the spices. Whisk in the eggs, one at a time, until combined, then stream in the cream and crème fraîche. Whisk until silky-smooth. Pour the filling into the cooled shell. 
2. Bake for 30 to 35 minutes, until puffed around the edges. It shouldn’t be set completely, with the center retaining a slight-wiggle to it. Remove and allow to cool completely