Prep ingredients: Rinse and drain beans. Trim scallions, then thinly slice, keeping dark greens separate. Trim ends from celery, then thinly slice. Scrub carrot, then halve lengthwise, and thinly slice into half-moons. Pick and finely chop 2 teaspoons tarragon leaves, discarding stems. Halve rolls lengthwise.

Sauté shrimp: Pat shrimp dry. Heat 1 tablespoon oil in a medium skillet over medium-high. Add shrimp and cook, stirring occasionally, until pink and cooked through, 2–3 minutes. Transfer to a plate.

Cook vegetables & sauce: Heat 1 tablespoon oil in same skillet over over medium-high. Add celery, carrots, and scallion whites and light greens; season with a pinch of salt. Cook, stirring occasionally, until vegetables are softened, 2–3 minutes. Add broth concentrate, beans, 1 cup water, and ¼ teaspoon vinegar, stirring to combine. Bring to a boil. Cook until carrots are tender, 2–3 minutes.

Make tarragon oil: Preheat broiler with top rack 6 inches from heat source. In a medium bowl, combine tarragon and 3 tablespoons oil; season with salt and pepper. Brush cut sides of rolls with some of the tarragon oil, then place on a piece of foil, oiled side up.

Toast rolls: Broil rolls on top oven rack until golden and crisp, 1–3 minutes (watch closely as broilers vary).

Finish & serve: Add shrimp to skillet with vegetables and beans. Cook, stirring, until warmed through, about 1 minute. Season to taste with salt and pepper. Spoon shrimp, beans, and vegetables into bowls; sprinkle scallion dark greens on top and drizzle any remaining tarragon oil over before serving, if desired, with toasted rolls for dipping.