Select a high-starch russet for the fluffiest mashed potatoes.
Preparation
Choose a starchy potato. The larger the starch granules, the more they swell while cooking, which produces the light, fluffy consistency of mashed potatoes. Select a high-starch russet for the fluffiest potatoes or a medium-starch Yukon gold for less fluffy potatoes with a slightly richer flavor. Peel six medium potatoes under cold running water and place them in ice water to prevent discoloration. Cut out all of the eyes and dark spots and cut the potatoes into 2-inch pieces to ensure even cooking.
Boiling
Place the potatoes in a large pan, cover them completely with cold water and bring them to a boil. Reduce the heat, place a lid on the pan and simmer for 20 minutes. Check from time to time to make sure the potatoes do not overcook and become watery and thin tasting. The potatoes are ready when a knife easily slides in and out without sticking. Place the potatoes in a colander to drain. Moisture makes potatoes gummy, so shake off any excess water and pat the potatoes dry with a paper towel.
Mashing
Some people like to use an electric mixer, but that tends to break down the starch and can cause the potatoes to become sticky and heavy. Use a potato masher or wire whisk to break up the lumps without breaking down the starch. Once the potatoes are smooth, add 1/2 cup of warmed cream and 1/4 cup of softened butter. Vigorously whip the potatoes to the desired fluffiness. Add salt and pepper to taste.