Slice the onion into thin half-moons.
1 large yellow onion
Generously apply salt and pepper to all sides of the coppa steaks.
2 coppa steaks, 1 tbsp kosher salt, 1 tbsp black pepper
Melt the beef tallow and half of the butter in a large pot or Dutch oven, over high heat on the range. Move a rack to the bottom part of your oven, and preheat to 350℉.
2 tbsp butter, 1 tbsp beef tallow
Add the steaks to the hot tallow. Allow space between the steaks to properly brown.
Cook until both side of each steak are well browned.
Remove the browned steaks to a glass dish.
Add the onions and balsamic vinegar. Sauté until tender.
1 tbsp balsamic vinegar, 1 large yellow onion
Stir in the flour, garlic, and thyme. Cook for a couple of minutes to brown the flour.
1/4 cup all-purpose flour, 3 cloves garlic, 1 tsp thyme
Add the dry red wine to deglaze. Scrape up the fond to incorporate into the sauce.
1 cup dry red wine
Preheat 3 cups of the beef stock in the microwave. Add the hot stock, plus the Worcestershire sauce, dark soy sauce, and cayenne pepper to the pot, and stir to incorporate.
1 quart beef stock, 1 tbsp Worcestershire sauce, 1 tsp dark soy sauce, 1/4 tsp cayenne pepper
Add the remaining knob of butter to the sauce. Allow it to melt and stir it into the sauce. The sauce should be fragrant, dark and silky.
Add the browned steaks and their juices back into the pot.
Cover and bake for two hours in the preheated oven.
After two hours, remove the lid. The meat should be very tender, and the sauce reduced and thickened. Carefully scrape up any stuck bits, and re-incorporate into the sauce. Add the remaining beef stock if necessary, to keep the sauce from burning.
Add the chopped parsley, and return to the oven with the lid removed.
1/4 cup flat leaf parsley
Remove from the oven. The sauce should be very dark, and the meat should be fork tender.
Add the chopped green onion.
1/4 cup green onion
Carefully add a steak to a wide, flat-bottom bowl. Serve with mashed potatoes, and a generous ladle of that delicious dark gravy. Bon Appetite!