Grate the ginger root and garlic clove - you only need the juice, it can be squeezed through a sieve or cheesecloth.
Thinly slice the chile, removing the seeds. Chop the cilantro (leave a handful of leaves whole) and grind in a mortar and mortar into a pulp with a large pinch of salt. Combine crushed cilantro, garlic ginger juice, chili and vegetable oil.
Toast a handful of peeled peanuts in a dry frying pan until fragrant, chop not too finely. Toss bok choy with mung bean sprouts, drizzle with dressing, toss, sprinkle with peanuts, and serve.