Preheat your oven to 350°F (180°C). Slice off the tops of whole heads of garlic, drizzle with olive oil, wrap in foil, and roast for 60 to 90 minutes until golden brown.

Heat a drizzle of olive oil in a large saucepan over medium heat. Sauté finely diced onion for 5 to 7 minutes until softened.

Add chopped fresh garlic to the pan and sauté for an additional minute until aromatic.

Pour in chicken or vegetable broth, scrape caramelized bits from the bottom, stir in white beans and fresh rosemary, bring to a boil, then simmer for 5 minutes.

Squeeze roasted garlic cloves into the soup mixture, and blend until smooth with an immersion blender.

Return soup to low heat, stir in grated Parmesan and lemon juice, season with salt and pepper to taste.

Ladle soup into bowls and serve immediately, garnishing with extra Parmesan or fresh rosemary if desired.