Cut roast into large chunks and add to bottom of slow cooker. Set aside.

Measure out all spices and set aside. Peel and cut onion into chunky strips. Heat a large frying pan over med/high heat. Add the oil and sauté onion until lightly caramelized and translucent, approximately 7-8 mins. Add spices and sauté for approximately 2-3 mins or until fragrant and oils start to release. Deglaze pan with rice vinegar.

Add onion and spices to slow cooker. Cut tomato and green onion into large chunks and add to slow cooker along with cilantro, soy sauce and broth. Turn slow cooker on high for approximately 6- 8 hours or for 2 hours on low on stovetop.

Once done remove beef chunks and set aside. Strain broth through colander.

Prepare noodles according to package.

Cut bok choy into 1/4's and blanch for 1 to 2 mins in boiling water. Remove onto plate.

In each individual bowl place a serving of noodles, broth, beef and bok choy. Garnish each bowl with approximately 1 tbsp Black Chinese vinegar, a drizzle of sesame oil, cilantro, red chili pepper flakes and extra soy sauce if desired.