Make the dough: combine all ingredients in your stand mixer and using the dough hook knead for 6 to 8 minutes or until a smooth dough forms. You can do this by hand as well, just stir to combine everything and knead on a surface for about 8 minutes until you have a smooth dough.

Shape the dough into a ball and place it in a lightly oiled sealed container in your fridge for 1 hour. After an hour, divide the dough into 4 or 5 equal-sized pieces. If you shape it into 4 pieces, the sandwiches will be considerably larger. Shape all your dough pieces into balls and place them in a sealed container in the fridge until ready to use. The dough will work after being in the fridge for up to 5 days.

If you're cooking immediately, leave a dough ball on the counter while you get the chorizo and onions ready.

Korean-style fire paste: add the gochugaru, gochujang, corn syrup, vegetable oil, soy sauce, minced garlic, and minced ginger to a small bowl and mix well. This is your fire paste that is added to the spicy mushroom gravy. It will not all be used in the gravy, but you can use this paste in any application where you'd want to marinate meat or add extra spice to a dish. Store in the fridge for up to a month. 

 Salisbury steak patties: mix ground beef, ketchup, hoisin sauce, beaten egg, and bread crumbs in a large bowl. Works best when you use your hands. Try not to overmix. When all ingredients seem incorporated, form your patties. I find this easiest to do with a parchment-lined sheet pan. 

Shape the meat mixture into four patties in shapes that are either a long rectangle (about 7 inches long and 2.5 inches wide). Or a half circle with a diameter of around 7 inches. 

Place beef patties covered with plastic wrap into the fridge while you make your sauce. 

Spicy mushroom gravy: add butter to a pan on medium heat. When butter has melted, add your diced onion and sliced mushrooms. Cook the mushrooms and onion for around 10 minutes until the mushrooms start to get soft. 

Add the two tablespoons of flour and stir in with the mushrooms and onion. When you can no longer see white flour (2 to 3 minutes) you can add the ketchup, Korean-style fire paste (that you made above), and beef broth. 

Raise the heat on the pan to high until the sauce starts to simmer. Add 1 teaspoon of cornstarch to a small bowl with 1 tablespoon of water. Mix to combine well. This is a cornstarch slurry. Once it's fully combined, add it to the pot and simmer for 10 minutes until the sauce has thickened.

Taste for seasoning and add salt and pepper if you think it needs some. If you are not immediately making a sandwich, you can store the sauce in the fridge for up to a week. If you are making a sandwich now, just move the warm sauce to the side. It will be used and warmed back up during sandwich assembly.

Sandwich time: when it's sandwich time, preheat your oven to 450 F (232 C). If you own a pizza steel or pizza stone, add it to the middle rack while the oven is preheating. If not, you can just add a sheet pan to the oven and let it preheat. 

Salisbury steak: at this point, if your sauce is still in a pan, you can go ahead and start cooking the beef. If you do not have another pan, pour your sauce into a bowl and put it aside until the beef is done. 

Add 1 beef patty to a pan over medium-high heat (if cooking more patties, just double, triple, or quadruple the amounts in the Sandwich assembly area. Cook each patty for 3 minutes per side. Once your patty is cooked, fully remove the pan from the heat and allow the patty to rest while the dough is baked. You will heat the patty again with sauce and cheese once the dough is ready. 

Dough baking: shape one dough ball on the counter with your hands into a circle around 7 inches in diameter. If you choose to make 4 dough balls instead of 5, you should shoot for 9 to 10 inches in diameter. 

Once you have a circle, add 2 teaspoons of olive oil to the dough and spread it all around evenly across the top of the dough. Add half of the shredded cheese on top of the oil on one side of the circle. Fold the dough over the cheese into a semicircle and place it on a piece of parchment paper. The oil helps keep the folded-over part from sticking to itself. This allows you to open it up when fully cooked.

Carefully with a spatula or your hands, transfer the dough onto parchment paper into the oven on top of the pizza stone/steel or hot sheet pan.

Cook for 4 to 5 minutes or until the top of the dough is getting puffy and the folded-over part is starting to separate. At this point the dough should be finished baking, but I suggest turning off the oven and turning on the broiler for 2 to 3 minutes to brown the top. Just be careful and don't walk away because it will burn quickly under the broiler. Pull it out when it looks dark enough for your tastes. 

Remove the cooked dough to a rack or plate to cool and get ready to sandwich. 

Sandwich assembly: place the pan with the Salisbury steak back on the stove over medium heat. Warm the patty up for a minute or two, and then flip. Immediately top the steak patty with the rest of the shredded cheese.

Add a couple of big spoonfuls of spicy mushroom gravy to the pan. Warm everything for an additional minute or two before spooning the sauce from the pan on top of the meat and cheese. 

Open the folded pizza dough very carefully because the inside will be hot. Add a few spoons of sauce from the hot pan, and then slide in the Salisbury steak, topped with cheese and the rest of the sauce. 

Garnish with chopped or torn cilantro and serve.