Chicken and Herb Dumplings Stew

Name: Chicken and Herb Dumplings Stew
Ingredients: 6 tablespoons butter.; 1 cup yellow onion, finely chopped.; 1 cup carrots, cut into matchsticks.; 1 cup celery, diced.; 4 cloves fresh garlic, minced.; 3 tablespoons all-purpose flour.; 12 ounces evaporated milk.; 32 ounces chicken stock.; 4 cups cooked chicken, shredded.; 1 tablespoon fresh thyme leaves.; 2 teaspoons black pepper, freshly cracked.; 2 cups all-purpose flour for dumplings.; 1 tablespoon plus 1 teaspoon baking powder.; 3/4 cup whole milk.; 4 tablespoons melted butter for dumplings.