Prep your base. Heat 1–2 tablespoons of olive oil in a large pot over medium heat. Add onion, celery, and carrots with a pinch of salt.
Cook 6–8 minutes, stirring, until the vegetables soften and smell sweet.
Add aromatics. Stir in the garlic, thyme, red pepper flakes (if using), and bay leaves. Cook 1 minute until fragrant. Don’t let the garlic brown.
Pour in broth. Add the chicken broth and bring to a gentle boil.
Taste and lightly season; remember you’ll season again later.
Poach the chicken. Slide in the chicken breasts. Reduce to a low simmer, cover, and cook 12–16 minutes, depending on thickness, until the chicken is just cooked through and tender.
Shred and rest. Transfer the chicken to a board. Let it rest 5 minutes, then shred with two forks into bite-size pieces.
Keep it juicy by shredding along the grain rather than across.
Cook the quinoa. While the chicken rests, stir the rinsed quinoa into the pot. Simmer 12–15 minutes until the grains unfurl and are tender.
Add beans and chicken. Return the shredded chicken and the white beans to the pot. Simmer 3–5 minutes to warm through and let flavors mingle.
Finish with greens and lemon. Stir in the spinach until just wilted, 1–2 minutes.
Add lemon zest and juice. Taste and adjust salt and pepper. The lemon should brighten the broth without turning it sour.
Herbs and serve. Turn off the heat and fold in parsley.
Ladle into bowls and garnish as you like—Parmesan for richness, chili oil for heat, or a spoon of Greek yogurt for extra protein and creaminess.