This is based on a recipe from the Williams-Sonoma Potato cookbook. These have been our "company" or "holiday" mashed potatoes for many years. They can be made up to 2 hours ahead: cover loosely and allow to stand at room temperature; then reheat gently over low heat, stirring often, just before serving.
07Squeeze each garlic clove into a small bowl and mash with a fork until almost smooth. You should end up with about 1/3 cup. Reserve any olive oil remaining in the baking dish.
08Pour 1-inch of water into a large pot and bring to a boil.
09Place the potatoes into a collapsible steamer basket and set the basket over the boiling water. (Do not allow the water to touch the bottom of the steamer basket). Cover and steam about 15 minutes, or until the potatoes are tender when pierced with a small knife. Transfer potatoes to a bowl.
10Empty the pot and wipe dry.
11Return the potatoes to the warm pot.
12Add the butter and 4 tablespoons of the roasted garlic and mash well with a potato masher.
13Add the 6 tablespoons milk, 1 teaspoon kosher salt, and 1/2 teaspoon pepper.
14Continue to mash, adding more milk, 1 tablespoon at a time, in order to reach the desired consistency.
15Taste and add more of the roasted garlic, if desired.
16Serve at once, drizzled with the reserved garlic oil.