Start with the onion. To clarify – cut the onion in half. You’ll finely mince one half and thinly slice the remaining half into thin rings or half-moons depending on which direction you sliced the onion.
Heat a large skillet to medium-high heat.
When it’s heated, add ½ tablespoon oil and sauté the minced half of the onion until softened. Keep your eye on this while you move on to the next step.
Meanwhile, in a medium bowl, mix the hamburger, breadcrumbs, egg, horseradish, half tablespoon Worcestershire and a little salt and pepper.
Add the softened onions from the skillet then turn down the heat on the skillet while you mix.
Combine these ingredients.
Divide this mixture into 4 portions and form oval shaped patties about ½inch thick.
Return your skillet to medium-high heat and add another ½tablespoon oil.
Place the patties into the skillet and cook 4 - 5 minutes per side, flipping once.
Set aside and keep warm.
In the same skillet, in the drippings from the beef, sauté the rings of onion and mushrooms until soft and golden brown.
Remove the onion and mushroom and set aside.
Add the broth and using a spatula or wooden spoon, stir, scraping up all the lovely, browned bits.
Mix the cold water and corn starch together until very smooth (no lumps!) and pour into the broth.
Bring to a simmer for 2 to 3 minutes, or until thickened.
Add the remaining ½ tablespoon Worcestershire.
Return the patties, onions, and mushrooms back to the pan and give it all a good stir to coat and warm up.
Let this simmer for a few minutes to let the flavors develop.
Serve with mashed potatoes and peas and carrots for the whole TV dinner vibe.