1. Melt butter in a large stockpot or Dutch oven over medium heat. Add onion, carrots and celery. Cook, stirring occasionally, until tender, about 3-4 minutes. Stir in garlic until fragrant, about 1 minute.
2. Whisk in chicken stock and bay leaves; season with salt and pepper, to taste. Add chicken and bring to boil; reduce heat and simmer, covered, until the chicken is cooked through, about 30-40 minutes. Remove chicken and let cool before dicing into bite-size pieces, discarding bones.
3. Stir in chicken and pasta and cook until tender, about 6-7 minutes.
4. Remove from heat; stir in parsley, dill and lemon juice; season with salt and pepper, to taste.
5. Serve immediately.