Roasted Garlic and Basil Smashed Potatoes

1/4 cup garlic cloves (about 6), unpeeled
4 large russet potatoes
1 cup milk, plus more as needed
3 tablespoons unsalted butter, softened
1 teaspoon olive oil
1/2 cup shredded fresh basil
Kosher salt and freshly ground black pepper

Preheat oven to 400 degrees.

Arrange garlic in 1 layer on a double thickness of foil and wrap tightly.

Roast the garlic and potatoes in middle of oven--the garlic will take 45 minutes and the potatoes will take 1 hour.

Unwrap garlic and cool slightly. Peel the cloves, mash with a fork, and set aside. (The garlic may be roasted and stored in the refrigerator, up to a week ahead.)

Combine the milk and butter in a large bowl.

Scoop the flesh from the potatoes into the bowl and smash using a potato masher.

Using a rubber spatula, mix the potato mixture and garlic together until creamy.

Fold in the basil and season with salt and pepper.