1 Large Potato, 1 Small/Medium Onion, 2 large leeks, 1 vegetable stock cube, salt & pepper, 1 large tablespoon of olive oil.
Chop onion finely, then fry gently in olive oil until soft. Chop potato then add to saucepan with a pinch of salt and pepper. Simmer gently for 5 to 10 minutes. Add leeks, 1 pint of water, and 1 vegetable stock cube. Simmer for further 15 minutes until potatoes are cooked. Mash and serve.