Heat oil in a large pan, add meat in batches and cook until browned all over; remove beef from pan.
Add onion to pan, cook stirring, until browned lightly.
Return steak to pan, add wine, water, juice, paste, stock cube, bay leaf and sugar. Bring to the boil, cover, simmer for 1¼ hours.
Add mushrooms, capsicums and green onions to pan. Cover and simmer for 15 minutes.
If you are going to eat it straight away, stir in the cornflour blended with 2 tablespoons of water, stir over heat until mixture boils and thickens. If freezing, do this step, if needed, when thawed.