Break the cauliflower into large florets. Trim off and discard the tough outer layer of the core, then cut the tender inside into 1 1/2-inch pieces.
Heat the oil in a heavy 6-quart pan over moderate heat until it shimmers. Add the cumin seeds and dried red chile and cook, shaking the pan, for 1 minute. Add the shallot, garlic, ginger, and fresh green chile and cook, stirring for 30 seconds. Stir in the turmeric, tomato and salt to taste.
Stir in the cauliflower and stock and cover the pan. Simmer gently until the cauliflower is tender, 15 to 20 minutes. (It's important that the cauliflower cook slowly; otherwise, the liquid will evaporate too quickly, you'll have to add more, and the cauliflower will turn soggy.)
Puree the cauliflower mixture in a food processor in 2 batches until smooth. Season to taste with salt and pepper.
Melt the butter in a 10-inch skillet over high heat and saute the ginger for 30 seconds.
Add the chestnuts, stirring and shaking the skillet, and season with salt. Saute the ginger and chestnuts until golden and caramelized and a little crisp around the edges, about 2 minutes. Transfer the ginger and chestnuts to paper towels to drain.
Reheat the puree over low heat and stir in the chives and cilantro. Serve the puree topped with the sauteed ginger and chestnuts.
Chef Floyd Cardoz, Tabla Adapted from One Spice, Two Spice