In a food processor, place the onion, garlic, ginger and jalapeno, if using, and process until smooth.
Place the oil in a 4-6 quart slow cooker turned on HIGH. Add the onion puree and stir in the mustard, fennel, cardamom, allspice, cumin, turmeric, and cayenne. Cover and let it cook on HIGH for 5 minutes.
Stir in the potatoes, cauliflower, kidney beans, tomatoes and stock into the cooker. Season with salt and pepper; cover and cook on LOW for 6 hours.
When the vegetables are tender, add the coconut milk and cook, uncovered, to incorporate the flavors, 10 to 15 minutes.