Blanch the cauliflower, and rinse in cold running water. Drain and set aside.
Grind the garlic, turmeric and cilantro root or stem together in a pestle and mortar, or spice grinder.
Heat the oil in a wok or large, heavy skillet. Add the scallions, and stif over high heat for 2 minutes. Add the Thai spinach, or greens, and stif for 1 minute. Set aside.
Return the wok or skillet to the heat, and add the mustard seeds. Stir until they start to pop, then add the turmeric mixture and the cauliflower. Stir until all the cauliflower is coated.
Serve with the spinach or greens on a warmed serving plate.