Boil tomatoes until skin separates; remove skin. Cut cauliflower and tomatoes into chunks.
In a heated wok, add oil and curry powder. Add water, salt, sugar, and mushroom seasoning; stir and bring to boil. Add cauliflower; stir to coat the cauliflower with sauce and cover the wok with a lid. Allow to simmer until cauliflower is tender. Add tomatoes. Add potato starch solution to thicken sauce. Add peas; stir and serve.