1. Rub the beef with the chile flakes, paprika, salt, and pepper. Cover and refrigerate for 1 hour and up to 24 hours.
2. Set the electric pressure cooker to saute. Heat 1 Tbs. of the oil, and then add a batch of the beef and sear until it's browned all over, about 2 minutes per side, adding more oil as needed. Transfer the beef to a plate and repeat with the remaining batches.
3. If the pot looks dry, add a bit more oil. Add the onion and saute until golden, 3 to 5 minutes. Add the garlic and ginger and saute for 1 minute longer. Add the beer or broth, gochujang, ketchup, soy sauce, brown sugar, fish sauce, and sesame oil.
4. Cover and cook on high pressure for 90 minutes. Let the pressure release naturally for 20 minutes, and then release the remaining pressure manually.
5. Transfer the beef to a plate and tent with foil to keep warm. Set the pressure cooker to saute and simmer the sauce for 15 to 20 minutes, until it is reduced by half or two thirds (remember that it thickens as it cools). Let the sauce settle and spoon the fat off the top. Serve the sauce alongside the beef.