Adjust rack to middle position and preheat oven to 425 degrees. Wash and dry all produce. Peel and halve carrot lengthwise; thinly slice crosswise into half-moons. Dice celery. Halve, peel, and dice onion. Mince or grate garlic. Trim, then thinly slice scallions, separating whites from greens. Halve ciabatta.

Heat a large drizzle of olive oil in a large pot over medium-high heat. Add carrot, celery, onion, scallion whites, half the garlic, and half the Italian seasoning. Season with salt and pepper. Cook, stirring, until slightly softened, 3-4 minutes.

Stir chickpeas, tomatoes, stock concentrate, and 11/2 cups water into pot. Bring to a boil, then reduce to a simmer. Cook until veggies have softened, about 15 minutes. Turn off heat; season with salt and pepper (to taste).

Place ciabatta on a baking sheet. Toast in oven until crispy, 3-5 minutes.

While ciabatta toasts, combine 2 TBSP butter and remaining garlic in a small bowl. Cover with plastic wrap and microwave until melted, 15-30 seconds. Once ciabatta is toasted, brush with garlic butter and sprinkle with half the Parmesan. Return to oven until cheese is melted, about 1 minute more.

Divide soup between bowls. Sprinkle with scallion greens and remaining Parmesan. Serve with garlic bread on the side.