Prepare the potatoes. Peel the potatoes and cut them into evenly sized chunks (about 2 inches each).
Boil. Place the potato chunks into a large pot and cover with cold water by about an inch. Add 1 teaspoon of salt. Bring to a boil over medium-high heat, then reduce to a simmer and cook until the potatoes are fork-tender, about 15–20 minutes.
Drain well. Drain the potatoes in a colander and let them sit for 2–3 minutes to allow steam to escape.
Mash. Return the potatoes to the pot. Add softened butter and begin mashing with a potato masher. For extra smooth potatoes, use a hand mixer on low speed.
Add cream. Gradually pour in the warm cream while mashing until the potatoes reach your desired consistency. They should be smooth and fluffy, not gluey.
Season. Stir in salt and pepper to taste. Add any optional mix-ins, like garlic, cheese, or herbs.
Serve warm. Transfer to a serving bowl and top with a pat of butter or a sprinkle of fresh herbs for presentation.