Prepare the spice paste by combining the grated ginger, ground cumin, ground coriander, turmeric, chili powder, and ½ teaspoon of salt in a small bowl.
Add ¼ cup of water and mix thoroughly until you have a smooth paste.
Set aside.
Place a karhai, wok, or large frying pan over medium-high heat and add the oil.
Once the oil is hot and shimmering, add the whole cumin seeds. They should sizzle immediately.
A few seconds after adding the cumin seeds, carefully add the cauliflower florets and diced potatoes to the pan.
Stir well to coat in the oil and cook for about 10 minutes, stirring occasionally, until the vegetables are tender-crisp and have developed golden-brown spots.
Pour the prepared spice paste over the vegetables.
Stir-fry continuously for 1 minute to cook the raw spices and coat everything evenly.
Add another ¼ cup of water to the pan, reduce the heat to low, and cover.
Cook gently for another 2-5 minutes, stirring now and then, until the vegetables are perfectly tender and the sauce has thickened, clinging to the vegetables. There should be no liquid left in the pan.
Taste for seasoning and add more salt if needed.
Serve hot with your favorite Indian flatbread or rice.
Do not overcrowd your pan. Give the vegetables enough space to make contact with the hot surface, which helps them brown and char rather than steam.
