| Preheat oven to 400°F |
| Slice 1/4 in off the top of the garlic head |
| 1 head garlic, top sliced off | wrap in foil, roast 400°F until soft, 40 min | squeeze the cloves from their skins | mash together | season |
| 1 Tbsp olive oil |
| 2 1/2 lb Yukon Gold or russet potatoes, peeled and cut in 2-in chunks | cover with cold water, boil until fork-tender, 15 to 20 min | drain, stir in the hot pot 1 min to dry |
| 1 Tbsp kosher salt, for the cooking water |
| 5 Tbsp butter | warm until the butter melts |
| 3/4 cup whole milk or half-and-half |
| to taste salt and black pepper |