Preheat oven 350 degrees F.
Place garlic on a piece of aluminum foil and lightly spray the garlic with olive oil cooking spray once. Wrap aluminum foil around the garlic to form a tight package. Roast for 45 minutes. Once garlic is cool enough to handle, remove from aluminum foil and set aside.
In a nonstick 10-inch saucepan, heat 1 teaspoon olive oil over medium-high heat. Add onions and saute until translucent, about 1 1/2 minutes. Add spinach and nutmeg and saute for 1 minute. Add chicken broth and bring to simmer; simmer for 1 minute. Pour mixture into a food processor, and then squeeze the garlic cloves from the head of roasted garlic, discarding the skin. Add all remaining ingredients. Pulse until creamy. Serve warm.