Use a pestle and mortar or a small blender to pound or blend the garlic and coriander roots and stalks into a paste. Add the peppercorns and continue to pound roughly.
Heat a little of the oil in a nonstick frying pan and gently pan-fry the bean curd, in batches, making sure there is a slight gap between the cubes. Fry each side for 1–2 minutes until lightly browned. Remove and keep warm. Add a little oil to the pan before cooking each further batch.
Heat the remainder of the oil in a wok or large frying pan and stir-fry the garlic paste over a medium heat for 3–4 minutes or until fragrant.
Add the pepper and stir-fry for 3–4 minutes, then add the bean curd, ginger, spring onions and soy sauce. Gently toss together for another 2–3 minutes. Taste and adjust the seasoning.
Spoon on to a warm serving plate and garnish with coriander leaves and chilli slices. Serve with boiled rice or spoon over noodles.