1. In a large pot, saute the onion, celery, and carrots in the olive oil over medium-high heat until softened but not browned, about 5 minutes. Add in the bay leaf, rosemary, thyme, salt, and pepper and stir until fragrant, about 1 minute.
2. Sprinkle the flour over the vegetable mixture, stir to combine, and cook for 1 minute. Whisk in the stock and bring to the boil, add the potatoes and peas, then reduce the heat to medium-low, and simmer for 20 minutes, stirring occasionally until potatoes are cooked through. Stir in the chicken and the sour cream (optional) and simmer for 5 minutes or until chicken is heated through.
3. If desired, top bubbling stew with Herbed Drop Dumplings. See instructions below.Dumplings:Â Sift together the flours, baking powder, dried thyme leaves, and salt. Add the milk and stir with a fork until just combined. Drop by tablespoon into boiling soup or stew. Cover, reduce heat to medium, and cook for 10-15 minutes or until a toothpick inserted into the center comes out clean.