Place the potato chunks in a large microwave-safe bowl.
Cover the bowl with a microwave-safe lid, leaving a small gap to allow steam to escape. Or cover with plastic wrap and pierce with a knife.
Microwave on high for 9 to 12 minutes, or until the potatoes are tender when pierced with a fork.
Carefully remove the bowl from the microwave using oven mitts.
In a separate microwave-safe container, heat the milk and butter together for about 30 to 50 seconds, or until the butter is mostly melted.
Mash the potatoes using a potato masher or electric hand mixer until smooth.
Gradually add the warm milk and butter to the potatoes, mashing to incorporate. Add salt and pepper to taste.
Serve hot as a delightful side to your main dish.