Spicy desi cauliflower soup

My 7-year old chose this from "vegetarian recipes", a book my husband bought in India last year.

1 medium sized cauliflower chopped
1 large white onion chopped
1 large potato peeled
1 large carrot peeled and chopped (I just decided to add this)
2 tsp corriander seed powdered (dhania powder)
2 tsp turmeric powder
4 cups vegetable stock (make note of whether it has salt in it)
1 inch ginger root, peeled and grated
1 clove garlic, crushed
salt
1 TBS olive oil
1 tsp mustard seeds
2 tsp jeera
1.25 cup plain fat free yoghurt

Oil in pan, add mustard seeds wait for it to splutter, add jeera seeds, grated ginger, crushed garlic, and then onion. Saute for atleast 5 minutes. Add all the chopped veggies, and sautee with 3 TBS water. After 2 minutes, add the stock, and bring to boil. Then, lower flame and let it simmer for 20 mnutes. Wait for it to cool for 10 minutes and add the yoghurt. If it's added when the temp is too high, it separates.

For the record, we made an odd assortment today, of vietnamese soft spring rolls, bok choy sauteed with mushrooms, and a fast pizza Ellie Krieger has on her website, using tortillas, cheese, arugula and red onion. I'll have to record these recipes here sometime.