Rinse the potato under the cold tap for 5 minutes to remove the excess starch from the outside of the potato, then add 1 tsp of salt per litre of water and bring to a gentle boil. Bring the potatoes to a boil from cold to avoid damaging the outside before the potatoes start cooking and become watery.
Cook for 30-40 minutes until tender. The length of cooking time will depend on the size of the potatoes.
Drain the potatoes and allow to drain dry in the colander. However, do not allow the potatoes to cool too much, as the potatoes will turn gloopy during mashing.
While the potatoes drain, heat half the butter over medium heat and slowly cook the leeks with a pinch of salt. When the leeks soften, add the garlic and cook for a minute. Set aside.
Wipe out the pan that cooked the potatoes, and slowly heat the cream and remaining butter until the butter melts.
Mash the potato with a potato masher or ricer in a bowl. A potato ricer will remove all lumps from the potato. Stir the leeks through the mash, and season to taste with salt & pepper.
