Peel and cut potatoes into even pieces. Leave as much or as little skin on the potatoes as you like.
Place potatoes, garlic, and the onion into a large boiling pot and cover with water.
Cook on high heat until the water begins to boil. Reduce the heat to medium-high, maintain a boil, and continue to cook for 10-12 minutes; until potatoes are fork tender.
Drain potatoes and return the potatoes to the pot.
Add butter, milk, cream, salt, and pepper to the pot and mix well with a hand mixer or potato masher.