Combine the first 3 ingredients in a small bowl to make the seasoning mix.
Heat the oil in a heavy 5-quart pot over high heat just until the oil begins to smoke, about 3 to 4 minutes. Add the onions, 1 cup of the potato cubes, the broccoli stalks and the mustard seeds. Cover and cook, stirring occasionally, for 10 minutes. Add ½ cup of the stock and stir and scrape the bottom of the pot thoroughly. Cook, covered, for 3 more minutes, then add the seasoning mix and another ½ cup stock. Scrape the pot bottom thoroughly, then add the remaining stock, the remaining potatoes and the coconut. Cook, stirring occasionally, until the potatoes are tender, about 12 minutes. Blend in the coconut milk and add the remaining ingredients. Cover and bring to a boil, then reduce the heat to low and simmer, stirring occasionally, until the vegetables are tender but still retain their beautiful bright green color, about 9 minutes. Serve hot as a side dish or chill and serve on a leaf of lettuce as an unusual appetizer or salad.