Peel and cut the potatoes into roughly the same size, about 2 inches. Add the potatoes to a large pot and fill it with cold water. Add a tablespoon of salt.
Bring the pot to a boil over high heat, then reduce it to a simmer. Cook for about 15 to 20 minutes or until the potatoes are fork-tender.
In a small saucepan, add the heavy cream, butter, and garlic powder. Heat for 3-5 minutes.
Drain the potatoes and return them to the hot pot. Let them sit for about a minute. This helps the steam escape, giving you a fluffy mashed potato.
Mash the potatoes using a potato masher.
Then add the warmed heavy cream mixture, cheddar cheese, monterey jack cheese, and cream cheese to the potatoes. Stir until combined. Add salt and pepper to taste.
Serve warm, topped with extra butter and chives, enjoy!