Char ginger and onion over direct flame.
Blanch chicken in salted boiling water.
Roast black cardamom, star anise, cinnamon bark, coriander seeds, and cloves in a skillet.
Rinse chicken in cold water.
Combine roasted spices, ginger, onion, chicken, sugar, kaffir lime leaves, fish sauce, and water in the slow cooker.
Cook for 8 hours on low.
Cook rice noodles in a separate pot.
Chop chicken into pieces.
Strain broth with a fine mesh strainer.