Heat the oil in a sauté pan over medium high height. Throw in the diced potato and cauliflower florets and fry for about 5 minutes. Parts of the potato and cauliflower will be browned and crusted, other sides will remain lily-white but this adds to the final flavour of the taste.
Remove from the pan and set to one side.
Turn the heat up to high and add a little more oil if the pan looks dry. Fry the Nigella Seeds, Bay Leaf, Cinnamon Stick, Cardamom Pods and Cloves until they start to crackle and smell fragrant. Take care because those Nigella Seeds really are little spitfires - they gob out miniscule balls of molten hot oil. All over your arms.
Put the potato and cauliflower back in the pan and mix well with the spices. Stir in the rest of the spices and cook for a minute more to allow all the flavours to mingle.
Pour over the water, bring to the boil, which won't take long because the pan is really hot, turn down to medium low and simmer, uncovered, until the potatoes are just tender.
Add the lemon juice.
Stir through the yoghurt/cream and the chopped tomatoes and simmer for another five minutes.
Taste for seasoning, adding salt or sugar if you feel it needs it.
Sprinkle with Garam Masala and chopped Coriander (optional) and serve.