In a medium sized bowl, add flour, sugar and salt and whisk together to combine.
Next add your butter cubes to flour and using your pastry cutter, cut the butter into the flour mixture until various sized crumbs appear.
Slowly add the cold water into the flour until a ball of dough forms. Start with a 1/4 cup and add more water if you need it. Knead the dough quickly to bring it together. Don't worry if there is any flour left in the bowl.
Remove the dough from the bowl and round into a bowl. Cover the ball tightly with plastic wrap and place in the refrigerator for 45-55 minutes to rest.
For the Filling
Add milk and butter to a medium pot over medium low heat. Once the butter has melted, allow the mixture to cool to room temperature.
While it cools, whisk together eggs, sugar, flour, vanilla and nutmeg in a medium sized bowl and set aside. Whisk in the milk/butter mixture until smooth.
Preheat the oven to 425 degrees.
Remove dough from the fridge and add a bit of flour to a working surface or clean counter and place dough on it. Using a rolling pin, quickly roll dough out to about 1/4-1/3 inch thickness and place in your pie plate.
Line the dough with parchment paper and add pie weights to your crust then bake for 10 minutes.
Next remove pie crust from the oven and reduce heat to 325 degrees.
Next pour your filling into the pie, brush the crust with an egg wash (just 1 egg and 1 teaspoon of water whisked together( and bake for 45-55 minutes or until pie jiggles just slightly. Sprinkle with additional nutmeg and serve. If you see that the crust is browning too quickly, add some foil to the outside or a pie shield to keep it from browning any further.
Make sure all of your filling ingredients are room temperature so the custard will set up.