Prebaking the quiche crust

Cup of Yum
1. Roll out the pie dough to about two inches larger than the diameter of your quiche pan, about ⅛ inch thick. Line the quiche pan, trim and shape the edge (see Tips and tricks).
2. Cover with plastic wrap and chill for at least one hour.
3. When you are ready to bake the crust, preheat the oven to 425°F.
4. To prebake the crust, line the tart or pie pan with parchment paper and fill with dried beans or pie weights. Push the beans down to the bottom of the crust and up against the sides.
5. Bake for 20 minutes, then remove the parchment and beans, and bake for 7 to 10 minutes more until all of the crust is golden. Check after a few minutes. If it is starting to puff up, prick the crust lightly with a fork, being careful not to go all the way through the crust.
6. Remove the crust from the oven and brush all over with egg white to seal. Let cool.

Quiche filling

1. Meanwhile make the quiche filling. Toss together the cubed butternut squash, oil, and ½ teaspoon of salt in a rimmed baking dish, and bake for about 20 minutes until the squash has softened and is only just starting to brown. Let cool.
2. Melt the butter in a frying pan over medium heat, and add the leeks and cook, stirring occasionally, until the leeks are soft and just starting to brown. Let cool.

Baking the quiche

1. Set the oven temperature to 375°F.
2. Add the cheese to the base of the quiche. Then add the squash and leeks. The vegetables should be level with the top of the crust. Save any extra filling to make mini quiches in buttered ramekins.
3. Whisk together the half-and-half, eggs, thyme, mustard, remaining salt, and pepper in a small bowl or a large measuring cup.
4. Transfer the vegetable-filled crust to your oven, and quickly but carefully pour the egg mixture on top of the squash and leeks until it comes very nearly to the top of the crust.
5. Bake for 35 to 40 minutes until the custard is no longer liquidy, but there is still a bit of jiggle.
6. Serve warm or at room temperature.