In a bowl, add the cauliflower and carrots and season with salt, pepper, half a tsp of turmeric, and a 1/4 tbs of garam masala. Mix well with a tbs of water. Put in a roasting dish and roast in a hot oven at 200c for about 12-15 mins until tender. Set aside.

Meanwhile, boil the potatoes in plenty of  boiling water (with a teaspooon of salt) till they are tender. This should take 8/10 minutes, but keep checking. Drain, set aside.

In a karahi (Indian wok) or a wide pan - heat 2 tbs of the oil. Add the cumin seeds and when they crackle, add the onions, garlic and ginger and brown a little. Add 4 curry leaves. Mix in the cooked cauliflower and carrots - use a wooden spoon and mix gently so as not to break the florets.

Add the peas, 1/4 tbs of garam masala and salt to taste. Stir fry it on medium heat. 

The peas will release enough water to scrape the spices sticking to the pan, use a few splashes of water if needed. Ensure the veg is cooked through but not falling apart. Turn the heat off, cover and turn to the potatoes. 

In a frying pan, heat 2 tbs of oil, and add the nigella seeds and 1/2 tsp of cumin seeds when hot. Add 4 curry leaves green chilli if using. 

Add turmeric, roasted cumin powder, garam masala paprika, salt to taste - mix lightly.

Now add the potatoes. Fry them, gently with a non stick spoon, taking care they don't break too much. They should be lightly browned and a little crispy on the edges.

In a serving dish, gently spoon in the cauliflower mix, then some potatoes, alternating till it is all in the dish. Dot with the butter if using. Sprinkle with coriander. Leave in a  warm oven if you need to prepare other things. 

Serve with hot rotis, raita and a little salad - red onion in vinegar is perfect for me!