In a large pot melt butter over medium heat. Add onion, carrots, and celery and cook for 3-4 minutes until tender.
Stir in garlic, parsley, and thyme and cook for 1 minute.
Add 1 cup of water, chicken broth, rosemary sprig, and chicken to the pot. Stir and bring to a boil over medium heat.
Once boiling reduce heat to a simmer, cover, and cook for 15 minutes.
Discard rosemary sprig and remove chicken from the pot. Shred chicken and return to the pot adding in the cauliflower rice or instant rice if using and salt and pepper.
Cook for 2 more minutes and stir in the lemon juice.
Notes
*Nutrition calculated using cauliflower rice.
Refrigerate leftover soup in an airtight container for up to 4 days. Chilled soup can be frozen in zippered bags for up to 3 months.
Defrost soup in the refrigerator overnight, then heat on the stovetop on medium low heat.