Gochujang cola pot roast: add 1 tablespoon of oil to a medium pot or pan over medium-high heat. Cut the chuck roast into 2 to 3-inch square pieces. Salt and pepper each piece.
Once the oil starts shimmering, add half of the pieces of beef and cook for 4 minutes per side. Flip each piece over and cook for another 4 minutes on the second side. Remove the meat and place it into a slow cooker while you cook the onions, garlic, and braising liquid.
Reduce the heat under the pot to medium.
Add the sliced onions to the pot where the beef was and cook for 3 minutes. After 3 minutes, add minced garlic and cook for another 1 to 2 minutes, stirring often.
Once the garlic has cooked for a couple of minutes add beef broth and cola and stir to combine everything.
Add all of the other ingredients for the gochujang pot roast and cook over medium heat until the liquid starts boiling, stirring frequently to make sure everything is combined.
Once boiling, turn off the heat and pour all of the braising liquid into the slow cooker with the beef and cook on high for 3.5 hours or low for 7 to 8 hours.
After the time has elapsed, with a slotted spoon, remove all beef pieces to a cutting board leaving the liquid still in the slow cooker. Break each piece of beef apart with two forks to break it into smaller pieces.
Add the beef back to the sauce and store in the refrigerator until it is time to make the sandwiches.
Pickled banh mi vegetables: slice the carrot, daikon radish, cucumber, and jalapeno into matchsticks or disks/rings.
Add all vegetables into a quart-sized mason jar and a pint-sized mason jar (or two quart-sized jars).
Add water, apple cider vinegar, and salt to a small saucepan over medium-high heat.
Bring the vinegar mixture to a boil. As soon as it starts boiling, stir the mixture, remove it from the heat, and pour it into the jars over the vegetables. This is obviously a hot pot pouring hot liquid so be careful. I typically do the pouring process in the sink so any spilled near-boiling liquid does not hurt anyone.
Close the jar lid and let it rest on your counter until cool.
Add to the fridge and enjoy some great pickled veggies over the next few weeks.
Toasting the bun: spread a bit of butter on both sides of the bun and toast in a medium pan over medium heat until both sides are golden brown and toasty. Move the bun to a cooling rack while you prepare the meat.
Warm the meat and cheese: wipe out the pan from toasting the bun and place back over medium heat.
Add a sandwich-sized portion of gochujang cola pot roast to the pan and cook for 3 minutes or until things are starting to get bubbly.
Add the mozzarella cheese and cook for another 3 minutes until the cheese starts to melt. Stir the meat in with the cheese to help the melting process.
When the meat is warm and the cheese is melted, it's time to assemble the sandwich.
Sandwich assembly: scoop all of the meat and cheese from the pan onto the bottom bun.
Top the meat with 2 or 3 forkfuls of pickled vegetables and close the sandwich with the top bun. Serve and enjoy.
Notes:
No slow cooker? If you do not have a slow cooker, you can cook this same recipe in an oven-safe pot or roasting dish with the lid on. You can set your oven to 375 F (190 C) and cook it for roughly the same amount of time as the slow cooker instructions (3.5 hours). The oven does allow more moisture to evaporate than a slow cooker so you may want to add just a little bit more beef broth and cola (like 1/4 cup each) and check it at the halfway point to see if it’s losing a lot of liquid. You just want to make sure that the beef is mostly covered up by the braising liquid.
Don't like spice? If you would like to tone down the spice, you can reduce the amount of gochujang and chili garlic sauce. Or you can buy a mild version of gochujang and skip the chili garlic sauce entirely.