Peel potatoes with a vegetable peeler. In a large saucepan, place potatoes in enough cold water to cover. Heat pan on stove over high heat until water boils. Reduce heat to medium-high and gently boil, without a lid, for about 25 minutes or until potatoes are soft when tested with a fork or skewer. Drain potatoes.

Meanwhile, coarsely chop spinach.

In a microwave-safe jug, microwave milk on high (100 per cent) for about 30 seconds or until hot.

Return potatoes to saucepan on low heat. Stir the potatoes for 1 minute to dry out. Remove from heat.

Add butter and milk to potatoes, and mash until smooth. Stir in spinach and cheese. Season.