Place the peeled, evenly cut Starchy Potatoes chunks in a large Pot and cover with cold water by at least 1 inch. Add a generous pinch of 6 tbsp 无盐黄油，分开——4 tbsp 用于捣碎，2 tbsp 用于上桌. Bring to a boil over high heat, then reduce to a steady simmer.

Cook the potatoes until completely tender and easily pierced with a Knife or skewer with no resistance, about 18–22 minutes. Drain thoroughly in a Colander and return them to the hot Pot. Let them sit uncovered for 1–2 minutes over low heat to steam off any excess moisture — this is key to a fluffy, non-watery mash.

While the potatoes cook, combine the 1 cup 全脂牛奶 and the white parts of the 1 束小葱（青葱）切成薄片，白色和绿色部分分开 in a small Saucepan. Warm over medium-low heat until steaming and just beginning to simmer around the edges — do not boil. Remove from the heat and stir in the green 1 束小葱（青葱）切成薄片，白色和绿色部分分开 tops. Let steep for 5 minutes so the 1 cup 全脂牛奶 absorbs the scallion flavour.

Mash the drained potatoes with a Potato Masher or ricer until smooth and lump-free. Do not use a Food Processor or Hand Mixer, as this will make the potatoes gluey.

Add 4 tbsp of the 6 tbsp 无盐黄油，分开——4 tbsp 用于捣碎，2 tbsp 用于上桌 to the hot mashed potatoes and stir until melted and incorporated. Gradually pour in the warm scallion 1 cup 全脂牛奶, stirring gently between additions, until the mash is creamy and smooth. You may not need every last drop — add it to your preferred consistency. Season with 1½ teaspoons 6 tbsp 无盐黄油，分开——4 tbsp 用于捣碎，2 tbsp 用于上桌 and ¼ tsp ¼ tsp 白胡椒, then taste and adjust.

Spoon the champ into warmed serving bowls. Make a well in the centre of each portion and place a pat of the remaining 6 tbsp 无盐黄油，分开——4 tbsp 用于捣碎，2 tbsp 用于上桌 inside. Serve immediately while the 6 tbsp 无盐黄油，分开——4 tbsp 用于捣碎，2 tbsp 用于上桌 melts into the mash.