Place potatoes in a large pot of cold water with 1 tsp salt. Cover and bring to a boil. This will allow the potatoes interior and exterior to cook at the same rate, prevent mushy exteriors.
Once tender, drain and place back in pot. Keep heat on to evaporate any excess water for about 1 minute.
Roughly mash potatoes, then pour in melted butter and mash until butter is well distributed. The butter will coat the starch molecules, so when the liquid is eventually added it won’t turn the potatoes gummy – this will keep them fluffier.
Add in remaining ingredients and continue mashing to desired consistency. Season to taste with remaining salt as needed.