Mix the sauce

• Combine the beef broth, brown sugar, sesame oil, rice vinegar, ginger, garlic, black pepper and soy sauce.
• Stir until the sugar dissolves.

Sear the beef

• Season the chuck roast with salt, pepper and garlic or your favorite seasoning.
• Heat the butter in a skillet over high heat and sear the beef in small batches for 1 to 2 minutes per side, building color without cooking it through.

Deglaze and load the slow cooker

• Transfer the beef to the slow cooker.
• Deglaze the skillet with a splash of the measured beef broth, scraping up the browned bits, and pour it into the slow cooker.
• Add the remaining broth and the sauce mixture and stir gently.

Cook low and slow

• Cover and cook on LOW for 4 to 5 hours or on HIGH for 2.5 to 3.5 hours.
• Start checking early so the thin beef stays tender without falling apart.

Thicken the sauce

• Mix the cornstarch with the cold water to make a slurry.
• Stir the slurry into the sauce and cook on HIGH for 15 to 20 minutes, until thick and glossy.

Add the noodles

• Slice the green onions into 1-inch pieces.
• Separate the precooked noodles and add them directly to the slow cooker.
• Toss everything together and heat on HIGH for 5 to 10 minutes.

Finish and serve

• Top with the sliced green onions, sesame seeds and chili crisp oil if you want heat.
• Serve immediately and avoid leaving the noodles on keep warm so they don't soak up the sauce.