Place potatoes in a microwave safe bowl with 1 inch of water and zap for 10 minutes until the potatoes are cooked through. Peel and cut in a dice.
Make the Balti Sauce:
Heat a skillet. Dry-roast the bay leaves, coriander, cumin, fennel, mustard, cardamom, cloves, bay leaves and chilies until they are slightly darker and fragrant, about three to four minutes,
Turn off the heat, remove the ingredients to a blender, and to the hot skillet add the turmeric, curry powder, onion powder, garlic powder and ginger powder. Stir a bit to roast in the hot skillet without turning on the heat. Add to the blender.
Add the vinegar, tomato and oil to the blender. Blend into a very smooth paste.
Make the Vegetable Balti:
Heat the oil in a wok. Add the onions, stir-fry over high heat for a couple of minutes, then add the green peppers and mushrooms.
Cook over high heat, stirring frequently, for about eight to 10 minutes or until the vegetables are cooked but still have some bite. Add the potatoes.
Add a third of the Balti sauce. Stir well, and continue to cook over medium heat for about five to seven minutes. Add salt to taste.
Garnish with the chopped spring onions. Serve hot.
Hot tip: this tastes even better the next day, when the flavors have had a chance to sit together and meld.