1. Place garlic and potatoes in a pot, cover with salted water. Bring to a boil, reduce heat to medium-high and cook until very soft, about 30 minutes. Drain well; return garlic and potatoes to pot. Stir over medium heat for 1 to 2 minutes to dry. Put through a ricer or food mill to puree, or mash with a potato masher for a lumpier texture. Stir in 3/4 cup warmed milk and butter, adding more milk if needed. Season well with salt and pepper. Keep warm in a heatproof bowl set over a pot of simmering water, stirring often.
2. Cook bacon in a large skillet over medium-high heat until crisp, 7 to 10 minutes. Drain on paper towels. When cool, chop into small pieces and sprinkle over potatoes just before serving. (Can be done up to 2 days ahead. Leave bacon whole, wrap it in plastic wrap and chill. Warm it in the microwave and chop it just before serving.)