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 and cook over medium heat until the liquid starts boiling, stirring frequently to make sure everything is combined.
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 all of 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 serve over rice, noodles, or mashed potatoes. Or turn it into a sandwich!
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.