Preheat your oven to 350°F (180°C). Place whole heads of garlic on a piece of aluminum foil, drizzle them with olive oil, wrap them tightly, and roast for 60–90 minutes.

Heat a tablespoon of olive oil in a large saucepan over medium heat. Add diced onion and sauté for 5-7 minutes until soft and translucent.

Once the garlic is roasted, squeeze the cloves out of their skins into the saucepan with the onions. Stir in chopped fresh rosemary and cook for about 1 minute.

Pour in broth and add white beans. Bring to a boil, then reduce heat, and let it simmer for 5 minutes.

Transfer soup to a blender and blend until smooth and creamy, or use an immersion blender.

Return blended soup to saucepan over low heat. Stir in parmesan cheese, lemon juice, salt, and pepper. Warm through and serve.