Mix all ingredients well and form 8 equal size patties.
Heat a large skillet. Place the patties in the skillet. Don't crowd. They'll shrink down some. If the patties don't sizzle when placed in the pan, then the pan isn't hot enough. Brown well on both sides. Remove and set aside.
Add onions and mushrooms to hot skillet. Cook, stirring occasionally, for 10 minutes or until the volume of vegetables has reduced by half. Add more cooking oil if necessary.
Add enough flour to the pan to soak up all the grease. Keep stirring until the grease and flour is well incorporated and the white is gone.
Slowly add liquid stirring or whisking constantly until all the liquid has been added. Keep stirring or whisking until the gravy starts to thicken.
Add the patties back in the pan. Spoon the gravy over the patties. Cover and simmer for 30 minutes.
Taste the gravy for seasoning and adjust as needed.
When done, remove the patties to a bowl and pour the gravy over. Granny served them in a bowl that looked very similar to the one I have.
Southern-Style Hamburger Steaks with Onion Mushroom Gravy. 3 ingredients hamburger steaks cooked in a flavorful onion mushroom gravy.