Preheat the oven to 450℉. Position the rack in the center.
In a 9-10 inch Dutch oven that’s 4-5 inches deep, cook the bacon. Use a slotted spoon to remove the bacon and place it in a bowl. Turn off the heat and set the Dutch oven aside.
Add the oil and sauté the beef until browned on all sides. Add it to the bowl with the bacon.
Add the sliced onion, carrot, and mushrooms to the oil to brown the vegetables.
Return the beef and bacon to the Dutch oven. Add in the salt and pepper and stir. Sprinkle flour over the top of the beef.
Place the uncovered Dutch oven in the oven and cook for 4 minutes. Toss the meat and cook for an additional 4 minutes. Remove the Dutch oven and place on the stovetop.
Reduce the oven temperature to 325℉. Move the rack to the bottom.
Pour the wine and beef stock into the Dutch oven. Add the tomato paste, garlic, and herbs. Bring to a simmer.
Cover and place the Dutch oven back in the oven and cook for 2 1/2 - 3 hours until the meat is fork tender.
While the filling is cooking, prepare the gluten-free pie crust.
When the meat is done, place the Dutch oven onto the stovetop. Increase the oven temperature to 350 ℉.
Skim the fat off the sauce. Simmer for a minute or two and skim off any additional fat. Remove the bay leaf.
Continue to simmer until the beef filling thickens and most of the liquid has been cooked out. In the bottom of a deep dish pie pan or individual baking dishes, add the braised onions if you are using them. Then pour the filling into the baking dish or dishes.
Top with the gluten-free pie crust. Use a fork to help seal the edges. Cut a circle in the center of the pie for the steam to escape. Mix up the egg wash. Use a pastry brush to brush the egg wash on top of the crust. Bake for 25 minutes.
Place under the broiler for 3-5 minutes to brown the crust further. Allow to rest for 5 minutes.