In a food processor, combine the 1 ½ cups flour, ½ tsp salt, and ½ cup chilled, cubed butter. Pulse for about 30 seconds or until it is a crumbly butter and flour combination
Combine 1 large egg and 2 tbsp chilled water, then add it into the food processor with the flour. Pulse again for another 30 seconds. The mixture should look crumbly but should form into a dough if pressed with your hands
Pour the crumbs onto a clean work surface and use your hand to press them into a ball. Wrap the ball in saran wrap and let chill in the fridge for about 30 minutes until it is firm.
Once chilled, lightly flour a clean work surface. Using a rolling pin, roll the ball into a circle, starting from the center and working outwards until the dough is large enough to fit in your pie/tart pan.
Transfer the crust dough into the pie/tart pan. Use your hands to gently press the bottom, making sure the dough reaches into the corners of the pan. Fold any hanging edges under, then use your thumb and forefinger to scallop the edge of the dough.
Chill the crust for about 15 minutes in the fridge and preheat your oven to 400 degrees.
After chilling the crust, use a fork to poke holes in the bottom of the crust.
Lay parchment paper over the whole crust (even up the sides). Then, fill the crust with dry beans (I used black beans, but you can also use pie weights or other baking beans). Bake for 15 minutes.
Remove the parchment paper and beans/weights. In a small bowl, whisk 1 large egg. Use a pastry brush to brush the egg wash over the entire parbaked crust. Put the crust in the oven for another minute until the egg cooks.
Add a layer of gruyere cheese (about 1 cup) to the bottom of the crust. Put the crust in the oven again for another minute or until the cheese melts on the bottom of the crust.
Remove the crust from the oven and reduce the oven temperature to 325 degrees.
In a large bowl, crack 4 large eggs and whisk to combine. Then add 1 ¼ cup heavy whipping cream, ½ tsp salt, ¼ tsp black pepper, and ⅛ tsp nutmeg. Whisk again to combine. Set aside.
In the crust, layer 1 cup cubed ham, then 1 cup chopped green onions. Pour the custard over the fillings, then sprinkle the remaining ½ cup gruyere cheese on top of the custard.
Place the custard in the oven and bake for about 45 minutes or until the edges are set and the center jiggles just a little.
When fully baked, remove the pan from the oven and allow the quiche to cool on the stovetop for at least 20 minutes before serving. Enjoy!