Heat oil in a thick-bottomed pan and add cumin and red chillies. When they begin to change colour add onions and sauté on medium heat for two minutes or till pink.
Add garlic and green chillies and sauté further for a minute. Add potatoes, sweet potatoes, carrots, cauliflower, tomatoes and salt along with two to three cups of water and cover and cook on low heat till almost done.
Add Worcestershire sauce, vinegar and sugar, stir and cook for another five to ten minutes till vegetables are done and water is reduced to less than half. Serve hot.