Mix beef, breadcrumbs, milk, Worcestershire, onion powder, salt, and pepper until just combined.
Form the mixture into four oval patties, about 3/4 inch thick. Chill 10 minutes if soft.
Heat olive oil in a large skillet over medium-high. Sear patties until browned, 3–4 minutes per side. Transfer to a plate.
Reduce heat to medium. Melt butter in the same pan. Add onions and cook until lightly caramelized, 6–8 minutes.
Stir in mushrooms and cook until they release moisture and brown, about 5 minutes. Add garlic and thyme; cook 30 seconds.
Sprinkle flour over the vegetables. Stir and cook 1 minute to remove raw taste.
Slowly whisk in beef broth and Dijon. Simmer, stirring, until the gravy thickens, 3–4 minutes.
Nestle patties into the gravy. Cover and simmer on low until cooked through, 8–10 minutes.
Taste and adjust seasoning. Sprinkle with parsley and serve hot with mashed potatoes or rice.
Notes
Swap mushrooms for bell peppers if you prefer, or add a splash of cream for extra-rich gravy. Leftovers keep up to 4 days refrigerated; reheat gently with a bit of broth to loosen the sauce.This recipe is an original creation inspired by classic Smothered Hamburger Steak Delight flavors. All ingredient ratios and instructions are independently developed.