Begin by making the pie crust. (Of course you can skip this step and use a pre-made pie crust from the store!)
In a medium bowl, stir together flour and 3/4 teaspoon salt.
Use your hands, a fork, or a pastry cutter to cut in the butter and shortening. Work it together until it resembles coarse crumbs. There should be butter chunks the size of peas.
Add 1/4 cup ice water and combine with a fork until it has mostly come together. Dust your hands with flour and knead it together in the in bowl a couple times, until it has come together. Stick it in the fridge while you make the filling.
Preheat your oven to 375 degrees F.
In a 10-inch iron cast skillet, heat 2 teaspoons olive oil over medium high heat.
Add the onions and carrots and saute for about 6-8 minutes, until the onions are translucent and the carrots are beginning to soften.
Add the ground beef and continue cooking over medium high heat for another 5-8 minutes, until the beef is well cooked and crumbled.
Tilt the pan and use a spoon to drain the grease from the pan. Or whatever method you like to use to get ground beef out of a skillet.
In a small bowl, stir together 1 cup COLD (or at least room temperature) beef broth and 1/2 tablespoon cornstarch until dissolved. (The broth cannot be warm when you add the cornstarch, or it will get lumpy.)
Stir the broth mixture into the ground beef, continuing to stir over medium high heat.
Add 1 teaspoon Worcestershire sauce, 1 teaspoon salt, and 1/4 teaspoon pepper.
Once the mixture has started to bubble, lower the heat to medium and cook for another 3 minutes, until the mixture has thickened a bit.
Add in 1 cup each frozen peas and hash browns (no need to thaw) and stir together. Turn off the heat and spread the beef mixture evenly in the skillet.
Sprinkle 1 and 1/2 cups cheddar cheese over the top of the beef mixture, don't stir. The second time I made this I used a few slices of cheddar cheese instead of shredding it, and I liked that even better!
Roll out the pie dough you already made onto a floured surface. Roll it into a circle that will cover your skillet, plus about 2 inches to hang over. (Mine was about 14-15 inches across.)
Have the tablespoon of milk, a pastry brush, and 2 tablespoons shredded cheddar ready to go.
Working quickly (because you want your pie dough to go into the oven as cold as possible) cover the skillet with the pie dough. Fold the edges underneath and use your fingers to quickly crimp the edges however you like.
Brush the top of the pie and the edges with milk. Sprinkle with a little bit of cheese. (Don't use too much, you want to be able to taste the flakiness on top of the crust. I used too much in the version I photographed.) Use a sharp knife to make 2-4 slits in the top of the pie to vent.
Place the skillet on a baking sheet just in case it bubbles over.
Bake in the oven at 375 degrees for about 30 minutes.
After 30 minutes, you may need to cover the edges of the dough so that it doesn't get too brown. Fold a large square of aluminum foil in half twice, then cut a circle out of the center. Unfold the foil and you should have a cover for the edges of your crust but not the center. Cover the edges of the crust well and continue baking for another 5 minutes or so, until the center of the crust is starting to turn golden.
Let the pie sit for 10 minutes before slicing and serving.