Blanch the onions in boiling water for 3 minutes. Drain well and set aside until cool enough to handle, then peel. Set aside.
Meanwhile, add the beans to the pan of boiling water and boil rapidly for 10 minutes, then reduce the heat and simmer for 20–25 minutes or until tender. Drain well and set aside.
Bring the stock to the boil, add the coconut cream and stir well to mix. Set aside.
Using a pestle and mortar, pound the ginger and garlic to a paste. Stir in the ground coriander, garam masala, turmeric and chillies until well blended.
Heat a large wok over high heat. Add 2 tablespoons oil. When hot, add the coriander, cumin and mustard seeds. Fry for 30 seconds or until the seeds give off their aroma. Use a slotted spoon to transfer the seeds to paper towel on a plate. Add the remaining oil and the spice paste to the wok. Reduce the heat to medium and stir-fry for 1 minute. Stir in the carrots, parsnips, potatoes and 2 tablespoons water, and stir-fry for 2 minutes.
Pour in the coconut stock and bring to the boil, stirring. Reduce the heat to low, cover and simmer for 5 minutes. Add the cauliflower, peas and onions. Cover and simmer for a further 5 minutes, stirring occasionally. Uncover and bring back to the boil, then boil for about 5 minutes or until most of the liquid has evaporated and all of the vegetables are just tender.
Add the cabbage, beans and fried spice seeds and stir-fry to wilt the cabbage. Add pepper and serve immediately, sprinkled with chopped fresh coriander, if using.