Soak the bread in the milk for 2 to 3 minutes. Add in the beef, Worcestershire sauce, and seasoning, mix very well with your hands until fully combined. Form the mixture into even oval patties.
Heat a non-stick pan on medium heat. Once hot, add the oil. Brown the patties on both sides to get a deep brown crust. Remove from the pan and set aside. Add the mushrooms, garlic, shallot, thyme, and sage. Sauté until the mushrooms start to soften. Stir in the flour.
Stir in the broth, kitchen bouquet, and add the Salisbury steaks back to the pan. Bring to low simmer until the sauce reduces, concentrates in flavor, and thickens to a creamy consistency. Season with salt and pepper to taste. Remove thyme sprigs before serving.
Serve with bread. Garnish with thyme.