Discard stems, wash, dry, and cut kohlrabi into small pieces. Also cut tomato, shallots and add to cut kohlrabi. Also discard the leftover stalk.
Heat oil in pan on medium heat. Once hot, add mustard seeds and wait for them to crackle. Now add cut veggies to the pan. Add salt, turmeric, chili powder, mix well, and set lid on. Repeat this process every 2 to 3 minutes (for a total of about 10 to 12 minutes), till the veggies are cooked. Add garam masala, mix well and let it cook for a couple of minutes.