Add the flour, sugar and salt to the bowl of your food processor (or a large bowl if your making the dough by hand).
Turn the food processor on low speed and add the chunks of cold butter one at a time while the food processor runs until all the butter is added and the mixture resembles coarse crumbs.If making by hand, use a pastry blender or your hands to work the butter into the dough until the mixture is crumbly. Try not to handle the butter too much (the heat from your hands will soften it) - use quick movements and don't worry if some larger chunks of butter still remain.
Add the lemon juice and the water slowly as the food processor runs on low, just until the dough comes together and pulls away from the sides of the bowl. Depending on the weather and even on the brand of flour, I use anywhere between 2 and 4 tablespoons of water. If making by hand, use your hands to form the dough gently and quickly using just enough water for the dough to come together.
Dump the rough dough onto the counter and form the dough into a disc shape and wrap in plastic wrap, placing it in the fridge to chill for 45 minutes or overnight.
After the dough chills, preheat your oven to 375 degrees Fahrenheit.
Remove the chilled pie dough from the fridge and let it sit for about 10 minutes before rolling. Roll out the disc of dough into a large circle using a rolling pin. Add a generous amount of flour to the rolling surface and to the rolling pin, to prevent sticking and cracking.
Peel the rolled out dough off the counter surface gently by rolling it backwards onto the rolling pin.
Transfer it to a 9-inch pie plate and gently press the dough into the bottom of the pie plate and over the edges (try for a 1-2 inch overhang if possible).
Trim any dough that hangs over the edge of the pie to 1-2 inches past the edge (try to keep the overhang amount even all the way around). Tuck any overhanging dough under and into the pie plate to create a clean edge. Creating a double layer around the edges also helps keep the pie crust from shrinking when it bakes.
If your pie plate has a wide edge, seal the edge of the pie by creating a fluted pattern - press into the edge of the pie from the outside with your left thumb and index finger while pressing into the edge of the pie from the inside with your right index finger. Do this all the way around the edge of the pie to create a fluted pattern (and see my tutorial HERE for how to create a beautiful fluted edge to your pies!)
Beat the egg and 1 tablespoon of water and brush it lightly onto the unbaked crust. Use a light hand while brushing - too much egg wash creates an eggy texture after baking.
Dock the unbaked crust with a fork several times on the bottom of the pie dish. This will prevent the crust from bubbling up and help it bake evenly.
Bake at 375 degrees Fahrenheit for about 20-25 minutes, or until the crust is a light golden brown.
Remove it from the oven and let it cool completely to room temperature.
For the filling:
Add the 1 cup strawberries to a small pot over medium heat, along with the cornstarch, sugar and lemon juice.
Let the mixture cook, mashing the strawberries really well as it cooks and thickens.
Cook until the mixture is slightly thick and gelatinous (looks like jam) and the strawberries have completely fallen apart.
Add the sliced strawberries to the pre-baked crust and pour the cooked strawberry mixture over them, tossing the mixture just a little bit to make sure all the fresh strawberries are coated in the cooked strawberry mixture. Smooth out the top as best you can.
Let the pie cool almost to room temperature and then add it to the fridge to chill until the filling is set (about 2-4 hours). It will be set enough to slice after chilling, but still juicy.
Slice and serve with whipped cream or ice cream.
To make this recipe even easier, use a pre-baked pie shell from the grocery store or bakery, or purchase a frozen pie shell and bake according to package directions. Then make the filling as directed above.