3 tablespoons unsalted butter
5 boneless, skinless chicken thighs (1 1/2 pounds), cut into 1-inch pieces
Coarse salt and ground pepper
1/2 bunch scallions, cut into 1/2-inch pieces
1 medium green bell pepper, seeded and diced medium
2 celery stalks, diced medium
2 medium carrots, diced medium
1 teaspoon dried thyme
1/4 cup all-purpose flour (spooned and leveled)
2 bottles pilsner or another light- or medium-bodied lager (12 ounces each)
1 can (28 ounces) whole peeled tomatoes
1 to 2 tablespoons red-wine vinegar
Cornmeal Dumpling Dough