To begin, wash your russet potatoes and peel the skins.
Cut the peeled potatoes into even-sized pieces, then add to a large Dutch oven.
Pour enough water over the potatoes to cover them, and add a good amount of salt to the water.
Boil the potatoes on high for at least 20 minutes, until they are very fork tender.
Meanwhile, in a small sauce pot, melt the butter and sauté the garlic on low heat until fragrant. Use a fork to smash the garlic cloves into the butter; this will infuse the flavor more. Pour in the heavy cream, and milk into the garlic butter sauce pot. Stir well, and continue to simmer.
When your potatoes are done, drain them and add them back to the pan - but remove the pan from the hot stove burner.
Season the boiled potatoes with salt and pepper.
Remove the garlic cloves from your pot and set aside. Slowly pour the warmed butter and milk onto the potatoes, using a potato masher to get a smooth texture. Stir in the sour cream using a wooden spoon, and top with optional fresh parsley or chives. Enjoy!