Begin by washing the potatoes thoroughly under cold running water. Scrub away any dirt or blemishes. There is no need to peel them; the skins add flavor and nutrients, but if you prefer peeled potatoes, you can peel them now.

Cut the potatoes into uniform pieces, approximately 5cm (2-inch) cubes. This ensures they cook evenly. Place the potato pieces into a large pot.

Cover the potatoes with cold water by about 2.5cm (1 inch). Add 1 teaspoon (6g) of salt to the water. This helps season the potatoes from the inside out as they cook.

Place the pot over high heat and bring the water to a rolling boil. Once boiling, reduce the heat to medium-high to maintain a steady simmer.

Simmer the potatoes for about 15-20 minutes, or until they are fork-tender. You should be able to easily pierce a potato cube with a fork or the tip of a knife with no resistance. Be careful not to overcook them, as this can make the mashed potatoes watery.

While the potatoes are draining, gently warm the buttermilk and heavy cream in a small saucepan over low heat, or in the microwave for about 30-60 seconds. They should be warm to the touch, but not boiling. This prevents them from cooling down the hot potatoes too much.

Return the drained potatoes to the empty pot. Place the pot back over very low heat for about 1 minute. This gentle heat helps to dry out any residual moisture from the potatoes, leading to a fluffier mash.

Remove the pot from the heat. Add the softened butter (115g or 1/2 cup) to the hot potatoes. Let it sit for a minute to begin melting.

Using a potato masher or a sturdy fork, mash the potatoes and butter together until the butter is mostly incorporated. Do not over-mash at this stage; some small lumps are acceptable.

Gradually pour in the warmed buttermilk and cream mixture, about 60ml (1/4 cup) at a time, while continuing to mash or stir. Mix until the potatoes reach your desired creamy consistency. You may not need all of the liquid, or you might want a little more, depending on your preference.

Stir in the finely chopped chives (30g or 1/2 cup), reserving about 1 tablespoon for garnish. Add the remaining 1/2 teaspoon (3g) of salt and 1/2 teaspoon (1g) of black pepper. Stir gently to combine.

Taste the mashed potatoes and adjust seasoning with more salt and pepper if needed. Serve immediately, garnished with the reserved chopped chives.