Clean cauliflower and chop the florets to desired sizes. Optional - heat 3 cups water in a large bowl, add cauliflower florets to the slightly hot water. Leave it for some time. Rinse them under running water and drain them.
Heat oil in a pan, on a low to medium heat. Add mustard and cumin. When they begin to sizzle add the curry leaves and fry for 30 seconds.
Add onions and green chilli. Saute until pink or golden.
Stir in ginger garlic and saute till a nice aroma comes out for about 30 to 60 seconds.
Then add tomatoes and salt. Saute until the tomatoes turn soft and mushy.
Add turmeric, red chilli powder, garam masala and coriander powder. Saute for 30 to 60 seconds until the masala smells aromatic.
Then add cauliflower florets and saute for 1 to 2 mins.
Pour ½ to 1 cup water or coconut milk and give a good mix. I used 1 cup water at this step. Young cauliflower releases lots of moisture, so be careful not to add a lot of water at one time.
Cover and cook until the cauliflower is tender but not mushy.
If needed add more water or coconut milk to bring the curry to a desired consistency. I added half cup coconut milk at this stage.
Taste the curry and add more salt if needed. Garnish cauliflower curry with coriander leaves.