Put the ribs in a large pot and cover with cold water. Bring to a boil and cook for 5 minutes. Drain and rinse the ribs under running water to remove the grey scum. Wash out the pot.
Add the cracked peppercorns to a dry pot over medium heat and toast for 1 minute until fragrant.
Return the ribs to the pot with the garlic bulbs, 1.8 liters of water, light soy sauce and salt. Bring to a boil, then lower to a gentle simmer.
Cover with the lid slightly ajar and simmer for 75 to 90 minutes, until the meat is tender and pulls away from the bone easily. Skim off any foam and excess fat as it rises.
Add the tofu cubes for the last 10 minutes. Taste the broth and add a pinch more salt or pepper if needed. It should taste clearly peppery and savory.
Mix the dark soy sauce and sliced chilies in a small dish for dipping.
Ladle ribs, garlic, tofu and broth into bowls, top with cilantro, and serve with rice and the dipping sauce on the side.