Bring a large pot of water to a boil with 1 teaspoon salt. Add potatoes; boil until easily pierced with a fork, about 10 minutes. Transfer potatoes to a strainer using a slotted spoon; rinse with cold water. Add cauliflower to boiling water; cook until easily pierced with a fork, 3 to 5 minutes. Transfer cauliflower to strainer using slotted spoon; rinse with cold water. Reserve 1/2 cup cooking liquid.

Combine 3 tablespoons water, curry powder, coriander, cayenne, and saffron in a small bowl until paste forms. Let curry paste stand until flavors blend, about 10 minutes.

Heat ghee in a stockpot over medium heat. Add cumin seeds; cook and stir until seeds begin to pop. Add onion and remaining 1 teaspoon salt; cook and stir until onions begin to soften, about 3 minutes. Add curry paste; cook and stir until fragrant, about 2 minutes more. Add lemon juice, reserved cooking liquid, potatoes, cauliflower, and garbanzo beans; stir well to combine.

Stir green peas, coconut milk, and cilantro into potato-cauliflower mixture; simmer until vegetables are heated through and mixture has thickened slightly, about 10 minutes.