I peel the russet potatoes and cut them into even-sized chunks (about 1 to 1½ inch). That ensures they cook evenly.
Place the potatoes into the pot, cover with 4 cups of cold water, and stir in the 2 teaspoons of kosher salt. Bring to a boil, then reduce heat, and simmer until they are fork-tender (about 15 minutes)
I pour the potatoes into a colander, then return them to the pot off the heat and let them steam for 2-3 minutes. This evaporates excess moisture.
While still hot, I mash the potatoes with the 2 tablespoons of room-temperature butter, working it in fully before adding liquid.
In a separate small saucepan, I gently warm the ¼ cup cream (or milk). Then I slowly pour it into the mashed potatoes while stirring, ensuring a smooth texture.
Finally, I taste and correct it with salt and pepper. I like to top it with a little extra pat of butter, or sprinkle fresh herbs before serving.