Halve the white onion and gingers. Place them on an ungreased tray in the topmost rack of the oven to broil at 220 degrees celsius for 15-20 minutes or until you see the outer layer beginning to turn charred and black.
Soak noodles in water for 20-30 minutes until soft and bendable. Boil for 10 minutes till it reaches your desired consistency.
Pour stock into a stockpot. Bring to a boil then simmer it for 40 minutes. Remove any scum that floats to the top.
Prepare thinly sliced beef slices
Add fish sauce
Place garnish and enjoy