In a large mixing bowl, combine ground meat, grated onion, chopped garlic, parsley, garlic powder, breadcrumbs, egg, salt & pepper.
Form the mixture into oblong patties (about ¾ inch thick) and set aside on a plate. NOTE: 4 patties are a hearty size; 1 per person. They also can be made smaller into 6 total patties.
Add the flour to a shallow bowl and season with salt & pepper.
Place a large skillet over medium to medium-high heat on the stove burner and add the oil. TIP: when the surface of the oil is rippling, it's hot and ready.
Lightly coat the Salisbury steaks in the flour, then carefully lower them into the hot oil using a spatula.
Cook the steaks for 4-5 minutes per side, until browned and crispy, and cooked through the middle. Internal temperatures: beef and bison 160 degrees F. Chicken and turkey 165 degrees F.
Remove the cooked steaks from the skillet, then place them on a plate and cover with foil to keep warm.
In the same skillet, add the onions & mushrooms. Cook until the onions have softened and started to caramelize, and the mushrooms are softened, stirring often.
Remove the cooked onions & mushrooms, and spoon them over the Salisbury steaks.