Preheat the oven to 425 degrees Fahrenheit (220 degrees Celsius).
Line a 9" pie pan with the crust and prick all over with a fork. Cover with aluminum foil and pastry weights and bake for about 15 minutes. Remove the foil and weights, then bake for about 5 to 10 more minutes, until browned.
Heat the oil in a heavy bottomed skillet, then cook the onion and pepper until they begin to soften--about 4 minutes. Add the garlic and cook for another minute or two, then add the ground beef and cook until browned, breaking it up often.
Stir in the tomato sauce, the oregano, salt, pepper, and bread crumbs, and remove from heat.
In a small bowl, beat together the egg and milk then whisk in the salt, mustard, and cheese, and set aside.
Spoon the beef evenly into the pie crust, then spread the egg/cheese mixture over the top, all the way to the edges.
Bake for about 20 - 25 minutes, or until the cheese topping is golden brown. (Keep an eye on the edges of the crust--if they begin to get too browned, make a foil ring and cover them up for the last 10 minutes of baking.)
Recipe Notes
Want to make a flavorful pie that everyone will talk about? Here are a few tips that I swear by;
If you use seasoned breadcrumbs, cut back on salt to avoid over-salting the pie -just a pinch would do.
Do not use pre-shredded cheese. It doesn't melt or taste as good. Plus, it contains some additives that aren't really healthy. Always grate your own cheese. Period.
Par baking the crust is crucial as it gives you an extra crispy pie crust that holds up to the stack of the toppings without getting soggy. You can even par-bake a day ahead if you wish -just bake, let it cool, then cover with a clean kitchen towel.
If the crust edges are hanging over the pan, tuck them in using your fingers before par-baking.
Place a cookie sheet covered with aluminum foil to avoid a mess in the oven when baking my pie.
Serving
For added fun, especially if you have guests, set up a table with bowls of toppings and let everyone add their favorite ones. My favorites are always caramelized onions, chopped dill pickles, sliced tomatoes, crumbled bacon, ketchup or sliced mushrooms. These extra toppings will take your pie to another level!