Preheat oven to 350 degrees
Sauté onions in olive oil until soft
Add ground beef, sea salt, garlic powder and pepper, and cook until no longer pink
Stir in beef broth, Worcestershire sauce, and cream, then stir in mixed vegetables
Grease or spray a 13 X 9-inch casserole dish with cooking spray, and add layer of potatoes, then half of the beef mixture, and some cheese
Top with another layer of potatoes, remaining beef mixture and more cheese
Top with remaining potatoes and more cheese, loosely cover with foil, and bake for 20 minutes. Remove foil and bake until potatoes are tender and dish is bubbly, about 45 minutes total
Top with more cheese if needed, remove from oven, and allow to rest for 5 to 10 minutes before serving