If not using leftovers, cook vegetables until tender: Place potatoes in a pot of boiling water and cook for approximately 5 to 10 minutes, until almost tender. Add cabbage and green veg and cook a further two minutes, until tender. Drain.
In seperate pan, heat 1 teaspoon of olive oil and cook onions until just starting to brown. Remove from heat.
In a large bowl, combine all cooked vegetables and toss in partially cooked onions. Add salt and pepper to taste. Give mixture a good stir to combine thoroughly.
In a large frying pan, heat the remaining two teaspoons of olive oil over medium high heat. Add mixture to hot frying pan. Cook for approximately 25 minutes, carefully turning the mixture halfway through cooking to brown both sides.