Heat a teaspoon of the oil in a wok over high heat. Add the mustard seeds and as soon as they start popping turn off heat and carefully add the rest of the oil.
Put heat to medium and add in all the other spices (cumin, coriander, turmeric, chili powder). Stir in the onions, ginger, garlic and bay leaf. Cook until the onions are tender.
Mix in the potatoes and “fry” them with the spiced oil. Add the peas. Add water. Cover and cook until the peas are tender, about 10 minutes.
Stir the tomatoes, sugar, and salt into the vegetable mixture. Continue cooking about 10 – 12 minutes. Garnish with cilantro.