Preheat a nonstick skillet with olive oil
Mix all remaining steak ingredients together in a large bowl. Form them into four oval-shaped patties
Cook patties for 3-4 minutes on each side until the outside is crisp, flipping just once. Move to a plate tented loosely with foil
Using the same pan, reduce the heat to medium. Add 2 tbsp of butter; allow to melt. Add mushrooms and onions, cooking until softened. Transfer to a plate
Add the remaining butter to the skillet and allow it to melt. Whisk in flour until well combined
Slowly pour beef stock and french onion soup into the pan, stirring frequently. Allow the mixture to come to a soft boil; then, turn the heat to low to simmer until it thickens into a gravy. Add black pepper; stir
Stir the mushrooms and onions back into the gravy. Then, place the steaks back into the gravy, spooning gravy over each patty. Continue cooking on low for another 10-15 minutes until the steaks reach 160 degrees