Melt butter in a medium pot over medium heat. Add onions and garlic and sautÃ© until onions are soft and translucent, about 3-4 minutes. Add in celery and carrots and continue to sautÃ© for another 3 minutes, stirring often.
Add stock, chicken, and Italian seasoning. Bring to a boil on high heat, then cover, reduce heat to low, and simmer for 20 minutes.
Remove chicken from pot and add orzo. Cook uncovered on medium high until the orzo is cooked through (about 10 more minutes), stirring occasionally. Meanwhile shred the chicken with a fork and then place back into the pot, while the orzo is still cooking.
Once orzo is cooked, stir in lemon juice, parsley, and dill. Season with salt and pepper, to taste.
Serve immediately with some extra lemon wedges and fresh herbs.
How to make with pre-cooked chicken: You can make this soup with leftover chicken or rotisserie chicken. Add it in when you are adding in the orzo.