– 2 tablespoons all-purpose flour, plus more for surface
– 1 package about 1 pound frozen puff pastry, preferably all butter, thawed
– 2 tablespoons unsalted butter
– 1/2 (1 cup) onion, diced
– 1 (1/3 cup) small carrot, peeled and thinly sliced
– 1 (1/3 cup) stalk thinly sliced celery
– 1 small Yukon Gold potato, scrubbed and cut into a 1/2-inch dice
– 1 1/4 cups low-sodium chicken broth
– 1 cup (2 oz.) packed coarsely chopped collard-green leaves
– 8 oz. (226 g) boneless, skinless chicken breast, cut into 1-inch chunks
– Coarse salt and freshly ground pepper
– 1 large egg, lightly beaten