In a skillet over medium heat, saute onion in butter until golden and soft.
In a large mixing bowl, combine beef, pork, sauteed onion, egg, breadcrumbs, milk, and nutmeg; season with salt and pepper and mix everything well with your hand.
Take a portion and form into a patty, then throw it forcefully from one palm of your hand to the other several times as if you are hitting the patty. This will enhance the texture of patty and hold its shape during the cooking. Repeat the rest of the patties.
Poke the patties with your finger in the center to leave indentation.
Heat skillet over medium heat, add some oil and drop the patties to sear the outside, about 2-3 minutes per side. Then reduce the heat to low and continue to cook. You can cover with a lid leaving a little opening for the steam to escape. This will ensure to cook the patties all the way. Remove the patties to a plate and keep warm.
To make the sauce; raise the heat under the skillet where you cook the patties, splash the red wine and scrape off any meat pieces left in the skillet with a whisk. Let the wine reduce in half.
Add the stock, ketchup, Worcestershire sauce, and the steak sauce. reduce the heat to low and let the sauce simmer to thicken. Drizzle the sauce over your steak and top with a fried egg on top (if you wish)
Serve the steak with steamed rice and vegetable (or salad).