Soak chickpeas in plenty of cold water overnight. The following day, drain and rinse them well. Place in large saucepan, cover with water and bring to a boil. Simmer until they are tender, about an hour. Drain and set aside.

Meanwhile, prepare chestnuts. Bring saucepan of water to a boil, drop chestnuts in and boil until cooked through, 25 to 35 minutes. (Test them after 25 minutes; see note.) When you are satisfied that they are cooked through, drain and peel the lot.

Add olive oil to saucepan large enough to fit all your ingredients, and heat over low heat. Add garlic and cook until fragrant, then add onion and cook for 10 minutes or until soft and translucent. Add passata, bay leaf, rosemary, hot pepper flakes, chickpeas and peeled chestnuts. Add 2 cups water and bring to a boil. Reduce heat and simmer for 30 minutes. Season to taste with salt and pepper.

Spoon into bowls and drizzle with olive oil. Serve with crusty bread on the side. If you reheat soup the next day, you may need to add a bit more water as it will thicken quite a bit once cooled.