Form the patties – Form the beef into 4 patties, slightly wider than the buns. Season both sides with Montreal steak seasoning (or seasoning of choice — salt and pepper is fine).
Preheat the griddle – Preheat the griddle to about 400°F. While it heats, add the mushrooms to the griddle with a little oil and start cooking them.
Cook the mushrooms – Cook the mushrooms for about 4 minutes as they begin to release their water.
Cook the burgers – Once the griddle reaches 400°F, place the burgers down. Cook for about 4 minutes, then flip.
Add butter and garlic to the mushrooms – After flipping the burgers, add the butter and garlic to the mushrooms and continue cooking them for a few more minutes while the burgers finish.
Finish mushrooms and melt the cheese – While the burgers finish cooking, toast the brioche buns on the griddle. Add the Parmesan cheese and Worcestershire sauce to the mushrooms and stir to combine. Place 2 slices of Swiss cheese on each burger and melt.
Assemble the burgers – Spread garlic aioli on the toasted bun, add the burger, then top with the steakhouse mushrooms. Serve hot.