Preheat the oven to 200°C (180°C fan). Pluck the basil leaves off the stalks. Add all the stalks and ½ of the basil leaves to a tall container. Add ½ of the dried tomatoes, 1Tbsp olive oil and 2Tbsp water. Blend with a stick blender until a paste forms.
Cut the bread into bite-sized pieces. Drain the chickpeas in a sieve. Toss the bread and the chickpeas on a lined baking tray with the dried tomato paste. Drizzle with 1Tbsp olive oil and sprinkle with some salt. Bake for 12–14min. until golden and crisp, mixing halfway though baking.
Cut the tomatoes into large chunks. Slice the leek into thin rounds.
Heat up a medium pot on medium-high heat. Add ½Tbsp olive oil and the leek to the pot and sauté for 4–5min. until softened.
Stir 1Tbsp of flour into the leek, then deglaze with ½Tbsp of balsamic vinegar. Add the tomato chunks to the pot and sauté everything together for 1min. Season with a large pinch of salt.
Add the passata and 50ml water to the pot. Turn the heat to medium and let the soup simmer for ca. 5min. Then add the cooking cream and let simmer for ca. 1min. Blend the soup to the desired creaminess. Adjust the consistency with water and season with salt to taste. Serve the soup garnished with the remaining basil leaves, the chickpeas and the croûtons.