Preheat your oven to 400°F (200°C). Slice the top off a whole head of garlic, drizzle it with olive oil, and wrap it in aluminum foil. Roast for 35–40 minutes until soft and golden.

In a large pot, heat a splash of olive oil over medium heat. Add the chopped onions and celery, sautéing for 5–7 minutes until tender and translucent.

Squeeze the roasted garlic cloves into the pot, discarding the papery skins. Stir in the chopped fresh rosemary and sauté for 1–2 minutes until aromatic.

Incorporate the drained cannellini beans, vegetable broth, bay leaf, salt, and black pepper. Bring to a boil, then reduce heat and simmer uncovered for 20 minutes.

Remove the bay leaf and blend the soup until smooth or your desired texture using an immersion blender.

Stir in a splash of lemon juice, adjust seasoning, and serve warm garnished with croutons or olive oil.