2 heads of garlic
2 tablespoons olive oil
1 cup mayonnaise
1/2 cup buttermilk
7 tablespoons freshly grated Parmesan cheese
2 tablespoons fresh lemon juice
3/4 teaspoon Worcestershire sauce

Preheat oven to 400°F. Cut top 1/2 inch off heads of garlic, exposing cloves. Place each on square of foil. Drizzle with oil, then enclose in foil. Place on oven rack; bake until garlic is tender, about 45 minutes. Open foil; cool garlic slightly.
Hold 1 head of garlic, cut side down, over medium bowl and squeeze, releasing roasted garlic pulp into bowl. Repeat with remaining garlic. Mash until smooth. Whisk in mayonnaise, buttermilk, Parmesan cheese, lemon juice, and Worcestershire sauce. Season to taste with salt and pepper. Cover and chill until ready to use, up to 2 days.

Simply pour this rich dressing over wedges of crisp iceberg lettuce or quartered heads of romaine for a salad, or use it as a dip for crudités.