For pesto: Preheat oven to 325-degrees. Cut half-inch off top of garlic head (without peeling) to expose tips of cloves. Place garlic cut-side-up on sheet of foil, and lightly drizzle with 1 tablespoon olive oil. Wrap garlic head in foil and place on rack in center of oven. Roast garlic until cloves have softened and garlic is aromatic, 40 minutes to 1 hour. Squeeze out cloves when cool enough to handle.
In a blender or food processor, blend together roasted garlic, basil, Parmesan, pine nuts and remaining oil until smooth, scraping down sides as needed, about 30-60 seconds; set aside.
For potatoes: Set steamer basket in large pot filled with 1-inch of water. Add potatoes and cover. Bring water to a boil over high heat and cook until potatoes are fork tender, about 10-12 minutes.
Transfer cooked potatoes to a serving dish, drizzle with pesto and top with grated Parmesan. Serve.