Early in the day or the night before, mix ground beef with half the rosemary, Worcestershire sauce, eggs, bread crumbs and season to taste. I seasoned with garlic powder, seasoning salt, fresh ground pepper. Cover and let sit in refrigerator for several hours. Before dinner, remove from fridge and seperate into four portions and form into patties.(or as many as you're serving). Measurements are approximate. Meat should be firm, not so full of liquid that it is mushy.
Brown onions and mushrooms in a a bit of olive oil and butter. (I used onions sauteed in butter from a previous night's dinner and didn't have to add any butter or olive oil to the pan for the mushrooms.) Set aside.
Gravy: Melt butter in skillet, then add flour or corn starch. Whisk until it is a paste. Slowly ladle in beef broth (sometimes helpful if you heat the broth before adding) and continue whisking to make gravy. Add remaining rosemary, season to taste with salt, pepper and garlic powder. Add mushrooms and onions and simmer on low heat, stirring occasionally.
Pre-heat seperate skillet on high heat. Brown the meat patties well on both sides. Do not cook through.
Remove meat from skillet and place in simmering gravy, make sure meat is submerged in gravy. (should have just a bit of bubbling from heat). Simmer on low for 15-20 minutes, or until cooked through.
Serve with sides of your choice but I strongly recommend mashed red potatoes. I also served with steamed broccoli and steamed white corn on the cob.