Pat dry steaks with paper towels; season steaks with garlic salt and pepper.
Heat vegetable oil and 1 tablespoon butter in a large cast iron skillet over medium-high heat.
Add steaks to the hot skillet and cook until browned and cooked to desired doneness; about 3 to 4 minutes per side for medium-rare steak. DO NOT crowd the skillet; cook two steaks at a time if skillet isn’t big enough.
Remove cooked steaks from skillet; set aside and keep covered.
Set skillet back over medium-heat and melt remaining butter.
Add in sliced onions and season with a pinch of salt; continue to cook for 10 to 12 minutes, or until onions are soft and caramelized. Stir frequently.
Stir in minced garlic and season with Italian seasoning; cook for 10 seconds.
Slowly add in beef broth and Worcestershire sauce; using a wooden spoon, scrape up the browned bits from the bottom of the pan. Bring mixture to a boil.
Whisk in heavy cream and cook for 1 more minute.
Reduce heat to medium-low; return steaks to the skillet and continue to cook for 2 more minutes, or until steaks are heated through, and sauce has thickened.
Remove from heat.
Garnish with parsley and serve.