Heat large pot over medium heat with some oil. Add celery, carrots, and onion and sauté until starting to soften, about 3 minutes. Add garlic and cook for an additional minute. Add butter and flour and whisk well for another minute.
Add chicken broth slowly, stirring well after each addition. Add seasonings, bouillon cube, and Worcestershire sauce.
Add chicken and bring mixture to boil. Cover with lid, reduce heat, and simmer until chicken is heat through, about 10 minutes. Stir in milk.
Combine flour, baking powder, and salt in a bowl. Make a well in the center and addmilk, sour cream, and melted butter. Stir until just combined.
When soup is simmering again, add teaspoon sized scooping of the dumpling dough directly into the soup pot. Spoon a little liquid over each dumpling. The dumplings will double as they cook. Cover the pot and simmer on low for 12-15 minutes. Remove lid, gently stir to break dumplings apart, and check the dumplings. If they're still doughy, cook a few minutes longer.
