1 tablespoon butter
  1 tablespoon extra-virgin olive oil
  ½ cup chopped onions
  1/8 cup milk
  1/8 cup heavy cream
  1/8 cup beef stock
  1 teaspoon Worcestershire sauce
  1 teaspoon chopped fresh thyme (or ½ teaspoon dry thyme)
  ½ teaspoon onion powder
  ½ teaspoon garlic powder
  ½ teaspoon salt
  ¼ teaspoon black pepper
  1 ounce of white bread, crust trimmed off (1/2 cup)
  1 egg, beaten
  1 pound good-quality 80/20 ground chuck
  ½ pound good-quality ground sirloin
  ½ pound good-quality ground pork

For the Mushroom Sauce:

  2 cups beef stock
  ¼ cup heavy cream
  Pinch of salt
  Few grinds black pepper
  ½ teaspoon chopped fresh thyme(or half that of dry)
  ¼ teaspoon Worcestershire sauce
  ¼ teaspoon Gravy Master
  3 ounces butter divided
  1 tablespoon extra virgin olive oil
  ¼ cup chopped onions
  8 ounces mushrooms sliced
  2 ounces flour

Directions

1. In a medium sauté pan, melt butter in olive oil and cook onions for three minutes over medium heat.
2. Remove from heat and add milk, cream, stock, Worcestershire sauce, thyme, onion powder, garlic powder, salt, pepper and the bread.
3. Mix to combine letting bread soak up all liquid.
4. Once mixture is completely cool, add beaten egg and stir again to dissolve bread and egg into mixture.
5. In a large bowl, combine three meats and add onion and bread mixture.
6. Gently work mixture with your hands but do not over work the meat.
7. Form into five equal sized football shaped patties.
8. In a medium sauce pan, heat beef stock, cream, salt, pepper, thyme, Worcestershire sauce and Gravey Master. Hold on medium heat.
9. In a large skillet, heat 1 ounce of butter and olive oil over medium high heat.
10. Once hot and frothy, add the five patties and cook about five minutes on each side.
11. Gently remove to a platter. They will not be fully cooked at this point.
12. Add the onions to the pan and cook over same heat for one minute.
13. Add the mushrooms and increase heat to almost high.
14. Cook for four or five minutes until mushrooms are browned and have absorbed the liquid.
15. Remove mushrooms to a bowl and set aside.
16. Reduce heat to medium and add the remaining two tablespoons of butter. Once melted add flour and cook for four or five minutes until raw flour smell is gone.
17. One third at a time add hot stock whisking with each third.
18. Add reserved mushrooms and stir with wooden spoon.
19. Add Salisbury steaks to sauce, along with any liquid from the platter and then spoon sauce over top of each steak.
20. Cover pan and cook on medium low for 15-20 minutes or until a probe thermometer reaches 140 degrees when inserted into the center of one of the steaks.
21. Serve steaks with mashed potatoes and spoon mushroom sauce over both.