Put the whole chuck roast in the crockpot. No cutting, no seasoning.
Pour the Korean BBQ sauce over it, then add the gochujang, garlic, and ¾ cup beef broth. Stir the liquid around the roast so the gochujang breaks up.
Cover and cook on HIGH 4 hours or LOW 7 to 8, until the beef falls apart with a fork.
Shred the beef right in the crockpot and pull out any big fatty pieces. It should be sitting in about an inch of sauce. If it looks dry, add a splash more broth.
Dump in the broccoli and push it down into the sauce. Cover, HIGH, 8 minutes.
Add the udon straight from the pouches and toss until the noodles loosen up. Cover, HIGH, 5 minutes.
Toss once more, snip the green onions over the top, and sprinkle with sesame seeds.
