Peel the potatoes, removing as many of the eyes as possible with the tip of your peeler. (If you prefer more rustic mashed potatoes, keep the skin on half of them.).
Submerge the potatoes in a bowl of cold water to keep them from turning brown while you are chopping them.
Cut the potatoes into similar-sized chunks so that they will cook evenly: the cubes should be about 1½ to two inches wide.
Submerge cubed potatoes into a pot of water that is large enough to hold the potatoes with enough water to cover. Add salt, if desired. Place the pot over a high heat and bring the water to a boil. Reduce heat to simmer.
Simmer, covered, until tender--about 15-20 minutes. A knife tip inserted into a potato should meet no resistance; if the potato clings to the knife, the potatoes need to cook longer. When potatoes are done, remove from heat and drain immediately.
Let the potatoes sit for a minute to dry and to allow any excess water to drain from the bottom of the colander. Meanwhile, heat the butter and cream in a small saucepan at a low temperature. (You can also use the microwave for this step.).
Return the cooked potatoes to the large pan and mash them with the back of a spoon, a food mill, or a potato ricer.
Gently stir in the warm butter and cream.
At this point, taste the potatoes for proper seasoning and adjust it to taste. Test for consistency, too: if the potatoes are too thick, add more cream. Other herbs and spices can be added at this point as well--chopped chives, Italian parsley, Parmesan cheese, crumbled bacon, roasted garlic, chopped scallions or creamed leeks are all delicious matches.
***To reduce the fat content of traditional mashed potatoes, use low-fat sour cream in place of butter, and milk or broth rather than cream.