In a large bowl, mix together the ground beef, 1/2 cup panko, 2 eggs, 4 tsp ketchup, 2 tsp Dijon mustard, 1 tsp oregano, and 1 tsp salt until combined.

Shape the mixture into 8 equal oval patties, about 3/4-inch thick.

In the big pan, warm 2 tbsp olive oil over medium-high heat; add the steaks and cook, about 3 minutes per side until they get a nice golden crust (reducing the heat if they're browning too much.) Transfer to a plate.

Reduce the heat to medium and in the same skillet with the drippings, add 2 tbsp butter. Once melted, add in 2 tbsp flour and whisk until combined and no lumps remain.

Reduce heat to medium-low and pour in the beef stock, whisking well. Add in 1 tbsp ketchup, 1 tsp Worcestershire sauce, and 1/2 tsp onion powder, whisking to combine.

Add in the mushrooms and onions, then simmer for about 5 minutes to thicken. Season with salt and pepper, to taste.

Add the partially cooked steaks back to the skillet and place in the gravy; cover and cook another 13 minutes until cooked through (with an internal temperature of 160 degrees F.)

Serve steaks with mushroom gravy on top.