Cut the potato into small cubes suitable for microwave cooking.

Place the potato cubes in a microwave-safe container, cover with a microwave-safe lid or plastic wrap, and poke holes in the wrap with a fork. Microwave for 4-5 minutes, checking and flipping halfway through.

Transfer the cooked potatoes to a large bowl and mash them with a masher or fork. No need to make them perfectly smooth at this stage.

Add butter, salt, and pepper to the mashed potatoes and continue mashing until smoother. Adjust the salt to taste.

Gradually add milk in two portions, mixing well each time to achieve the desired consistency. Aim for a slightly runny texture as the starch will thicken it over time.