Prep your veggies by using a mandolin to slice carrots and celery. Using a mandolin will ensure that your soup will cook in under 30 minutes. Otherwise, unevenly sized veggies may cause the soup to take significantly longer to cook! Alternatively, you can dice them.
Melt butter or oil in a large stockpot or dutch oven over medium heat. Add onion, carrots, celery, and garlic. Cook, occasionally stirring, until tender, about 5-7 minutes.
Add chicken broth, bay leaves, salt, pepper, chicken, and quinoa. Bring to a boil, reduce the heat, and simmer, covered, until the chicken is cooked through and the quinoa is fluffy about 20-30 minutes.*
Remove the soup from heat and then remove the chicken, dice, and return to soup—salt and pepper soup to your final taste. Garnish with fresh parsley and lemon juice. Serve immediately.
Notes
To freeze chicken quinoa soup: Option 1: Freeze this soup after it's completely cooled in a freezer bag or freezer-safe container. Make sure to leave at least ⅓ of the container empty because liquid expands when it freezes. Option 2: Since this soup contains a huge amount of broth (thanks to the quinoa needing to soak so much of it up), you can freeze this soup prepped with or without the liquid. If I were going to freeze this soup, I'd probably freeze it with just four cups of broth so that I didn't have to find a container or multiple containers to hold 12 cups of liquid. Then, I'd write on the bag, "add 8 cups of chicken broth for cooking." Freeze together:
onion
carrots
celery
garlic
bay leaves
chicken thighs
uncooked quinoa
salt
pepper
4 -12 cups of broth
To cook - defrost under refrigeration. Once it's defrosted, dump the whole thing in a slow cooker or a large stock pan. In a slow cooker, cook for 4-6 hours on high or 6-8 hours on low until the chicken is cooked through. In a stock pan, bring to a boil, then reduce the heat and simmer, covered until chicken is cooked through and quinoa is fluffy.