Add the ground turkey, salt, pepper, garlic, ketchup, Worcestershire sauce, steak sauce, egg and breadcrumbs to a large bowl. Mix together until all ingredients are incorporated.
Separate the ground turkey mixture into 4 patties. Shape each patty into an oval shape. Like an elongated burger. Place the patties on a baking sheet or plate.
Heat the oil in a large, deep, non-stick skillet over medium-high heat. When the oil is very hot – but not quite smoking, add the turkey patties. Cook the patties for about 2-3 minutes, per side until they are browned.
Remove the skillet from the heat and lower the burner to medium-low. Remove the patties and place them on a plate or pan. Keep them warm by covering loosely with a piece of aluminum foil, and/or place the plate in the microwave or oven. They stay nice and warm in an enclosed space away from drafts. Don’t worry if the ground turkey steaks are not cooked through, they will finish cooking in the gravy.
Drain the excess oil but do not wash or wipe the skillet. Place it back over medium-low heat and add the butter. When the butter is melted and foamy add the onions and sliced mushrooms. Cook gently for 4-5 minutes, stirring frequently.
Add the flour to the onions and mushrooms, stir to combine well and cook for 1-2 minutes, stirring frequently.
Raise the heat to medium and add the chicken broth, Worcestershire sauce, ½ teaspoon salt and black pepper. Stir, while gently scrapping the bottom of the skillet as you go.
When the sauce is simmering, add the patties back to the pan (it will take about 5 minutes to come to a simmer).
Bring the liquid back up to a simmer (just 1-2 minutes), lower the heat to medium low, cover and continue cooking, at a simmer for 20 minutes, stirring occasionally, and flipping the steaks at least 2 times during the cooking time.
Uncover the skillet for the last 5 minutes of cooking to thicken the gravy further, if needed. Keep the gravy at a simmer, raise or lower the heat as needed.
The internal temperature of the turkey Salisbury steaks needs to be at least 165°F at the thickest part of the largest piece. Use an instant read thermometer to make sure they are up to temperature. If it’s not, continue cooking for 5-10 minutes and check again.
Taste the gravy and add salt if needed. As a reference we added ¼ teaspoon to ours.