Line a tray with wax paper and set aside.
In a bowl, mix ground beef, egg, cracker crumbs, Worcestershire sauce, salt, onion powder, and black pepper.
Shape into 4 patties, place on the tray, cover, and refrigerate for at least 1 hour or overnight.
Heat butter and oil in a skillet over medium-high heat. Cook patties for 3-4 minutes per side until browned. Remove and keep warm.
Add more butter to the skillet, then cook mushrooms for 5-7 minutes. Add garlic and stir for 30 seconds.
Stir in condensed soup and milk, then simmer on low for 5 minutes, stirring often. Add parsley.
Return patties to the skillet, spoon gravy over them, and warm on low heat.
Garnish with fresh parsley and serve immediately.