Prepare and Boil the Potatoes: Start by peeling and quartering the potatoes so they cook evenly. Place them in a large pot, then fill with enough cold water to fully cover them. Bring the pot to a rolling boil over medium-high heat, then reduce to a gentle simmer. Cook for about 15–20 minutes, or until the potatoes are tender enough for a fork to slide in easily.

Drain Completely: Once cooked, carefully pour the potatoes into a colander. Let them drain fully for a minute or two to remove excess moisture. This step is crucial for keeping your mashed potatoes light and fluffy rather than watery.

Begin Mashing: Transfer the drained potatoes into a large mixing bowl. Using an electric mixer on low speed, beat them for about 30 seconds, just until they start to break apart. Avoid overmixing at this stage to prevent a gummy texture.

Add Butter and Seasonings: Drop in the room-temperature butter along with the salt and white pepper. Mix gently until the butter melts into the warm potatoes, enhancing their flavor and creaminess.

Incorporate Cream and Sour Cream: Add the sour cream, then slowly pour in the heavy cream while the mixer runs on low. Continue mixing only until everything is well blended and smooth.

Finish with Cheese and Serve: Stir in the shredded white cheddar by hand, allowing the heat of the potatoes to melt it. Serve immediately while hot for the best flavor and texture.