If you are using salted butter, you’ll want to reduce the amount of added salt. This recipe calls for 3 teaspoons of kosher salt for 4 lbs of potatoes. Kosher salt is a coarser texture than table salt, so be sure to know the substitutions if a recipe calls or one or the other. If a recipe calls for Kosher salt, use 1/4 teaspoon less of table salt per teaspoon of salt. If a recipe calls for table salt, use 1/4 teaspoon more of Kosher salt per teaspoon.