Unroll the pie crust into a 9-inch dish, crimp the edges, and pre-bake at 400 degrees for 8 minutes so the bottom sets.
Brown the ground beef in a skillet over medium-high heat until no pink remains to ensure the meat is fully cooked.
Drain the excess grease from the skillet completely so the pie filling does not become overly oily and soggy.
Stir the ketchup, mustard, Worcestershire sauce, salt, and pepper into the beef to create that signature burger flavor.
Spoon the seasoned beef mixture directly into the pre-baked pie crust to build the savory base of the dish.
Top the beef evenly with shredded cheddar cheese and half of the diced red onions so the cheese can melt into the meat.
Bake at 400 degrees for 15-20 minutes until the crust is deeply golden and the cheese is fully melted and bubbling.
Remove from the oven, garnish with remaining red onions and parsley, and let rest for 5 minutes before slicing to serve.
