Heat the oil in a large skillet or sauté pan over medium-high heat. Add the ground beef and salt. Stir well and arrange in one layer. Cook for 3 minutes.
Stir well. Cook for 2 minutes (or until browned) while stirring and breaking up any large pieces.
Take the skillet off the heat. Remove the ground beef with a slotted spoon and place on a plate.
Drain most or all the excess grease in the skillet but do not wash or wipe.
Place the skillet back over medium heat then add the butter. When it is melted and foamy add the onions and mushrooms. Cook them for 5-6 minutes or until the onions start to soften. Stir occasionally.
Next, add the garlic and black pepper. Cook for 1 minute, stir often.
Add the flour and cook for 1½ -2 minutes, stir almost constantly.
Slowly add the beef broth while stirring briskly and gently scraping any bits off the bottom of the pan. Continue adding and stirring until the flour dissolves. Then stir in the Worcestershire sauce.
Return the browned ground beef to the skillet. Stir well to combine with the sauce. Raise the heat to high and bring the sauce to a boil.
Then, lower the heat to medium-low, cover, and cook the ground beef and mushrooms for 20 minutes. Stir occasionally and keep the sauce at a simmer. Raise or lower the heat, as necessary.
Taste and add salt if needed. As a reference we added ⅓ teaspoon to ours.
Garnish with chopped parsley and serve with mashed potatoes, vegetables, rice, or warm crusty bread, if desired.