• Preheat oven to 400 °F/200 °C with the rack in the center of the oven. Grease a 9-inch (23 cm) round quiche/tart pan preferably with a removable bottom.
• To make the pastry in a food processor: Add the flour, butter and salt. Pulse until you get the texture of fine breadcrumbs. Add 1 tablespoon of cold water. Pulse a few times until you start to see the dough come together, adding a little water as needed. Remove the lid and grab a little dough, if it holds together (without being sticky) it is done. If It crumbles pulse more adding small amounts of water. Test again using the squeeze test.
  
• To make the pastry by hand: Add the flour, butter and salt to a large bowl. Using your fingertips (or a pastry cutter) rub the butter and flour until it resembles breadcrumbs. Add a little of the water and mix using a fork until the it starts to come together and holds together when pressed in your hand. You may not need all of the water.
  
• Pour the dough onto a lightly floured surface and form into a flat disk. Wrap in plastic wrap and refrigerate 30 minutes. .

For the filling:

• To a sauté/frying pan, cook the bacon over medium heat. Drain and set aside. Keep bacon fat in pan.
• Return the pan over medium heat and add the mushrooms and squash, and cook until they start to soften. Add the leek and cook until the squash is tender when pierced with a fork, do not brown. Stir in the sage, salt and pepper. Turn off the heat and set aside. 
• To a mixing bowl add the eggs and milk, whisk until combined. Add the nutmeg, salt, pepper and whisk until combined.
• Add the bacon, leeks, mushrooms and butternut squash to the milk and eggs and mix well. Stir in the cheddar cheese. Set aside.
• Remove the pastry from the refrigerator and roll out onto a lightly floured surface, larger than the quiche pan.
• Roll the pastry over the rolling pin and lift into the pan. Pressing the bottom firmly and up the sides. Make the pastry slightly higher than the pan (don’t pull) to allow for it shrinking slightly during baking.  Don’t worry if the pastry cracks, you just want a nice even crust. Use your fingers to press out any cracks. Keep any extra dough in case you need to make patches.Cover the pastry in parchment paper and fill the center with dried beans or uncooked rice. This weighs down the pastry and prevents the bottom from puffing too much.
• Place the tart pan on a large baking sheet/tray or cookie sheet. This helps with moving it in and out of the oven, especially if you’re using one with a removable bottom.
• Lightly place a sheet of parchment paper inside and over the edges of the crust. Fill the center with dried beans/peas or uncooked rice.
• Bake the crust for 10 minutes.  This is to ‘blind bake’ the crust (without filling) to help the cooking process of the bottom of the crust so it is not raw when baking with filling. The dried beans are to weigh the bottom down so it doesn’t puff.
• After 10 minutes, remove the crust from the oven and remove the parchment paper and beans/peas or rice.
• Return the crust back to the oven for 5 more minutes. Remove from the oven. 
• Allow the crust to cool for a couple of minutes. Turn the oven down to 350°F/180°C. Lowering the temperature allows the filling to cook evenly without overcooking the crust.
• Mix the bacon into the leeks, mushrooms and butternut squash. Sprinkle evenly onto the bottom of the crust. Top those with an even layer of cheddar cheese. This is provides a barrier and helps prevent the liquid from  making the crust soggy Pour over the egg mixture and use a fork to lightly make sure the vegetables are evenly distributed. Top with an even layer of grated Parmesan cheese. 
• Bake for about 30 minutes, or until set and slightly golden brown. Time will depend on your oven. Remove and allow to cool for 10 minutes on a wire rack before removing from the pan and slicing. See my handy way of removing quiche and tarts from a removable bottom pan in the photos and description above and in the video.