In a large bowl, combine the ground beef, breadcrumbs, egg, ketchup, Worcestershire sauce, salt, and pepper. Mix gently with your hands until just combined, being careful not to overwork the meat.

Divide the mixture into 4-6 portions and shape each into an oval patty about 3/4 inch thick.

Heat 1 tablespoon of olive oil in a large skillet over medium-high heat until shimmering. Add the patties in a single layer without overcrowding (work in batches if needed).

Sear for 3-4 minutes per side until deeply browned. Remove patties to a plate and set aside.

Reduce heat to medium. Add 1 tablespoon of butter to the skillet and melt. Add sliced onions and cook for 5-7 minutes, stirring occasionally, until soft and translucent, scraping up any browned bits.

Add sliced mushrooms and a pinch of salt. Cook another 5-7 minutes until mushrooms have released their moisture and begun to brown.

Stir in minced garlic and cook for 1 minute until fragrant.

Sprinkle flour over the vegetables and stir constantly for 1 minute.

Gradually pour in beef broth while whisking continuously to prevent lumps. Stir in soy sauce.

Bring gravy to a simmer and cook until thickened, about 2-3 minutes. Season with salt and pepper to taste.

Return the seared patties (and any juices) to the skillet, nestling them into the gravy.

Reduce heat to low, cover, and simmer for 10-12 minutes until patties are cooked through and tender.

Garnish with chopped parsley before serving.