Heat olive oil in a large pot over medium-high heat. Add diced onion and cook 2-3 minutes until softened and fragrant, then stir in minced garlic and cook another 30 seconds.
Add sliced carrots and chopped celery to the pot. Stir constantly for 2 minutes to coat vegetables with oil and allow aromatics to deepen their flavors before adding liquid.
Pour in the cubed chicken breast and stir until partially coated with the aromatic oil base. Cook for 1-2 minutes without letting meat brown completely—we're building flavor, not searing here.
Add the chicken broth, diced tomatoes with juices, butternut squash cubes, thyme, sage, and bay leaf. This cozy 30 min fall soup dinner comes to a boil quickly when you maintain medium-high heat. Bring to a rolling boil for 1 minute, then reduce heat to maintain a gentle simmer.
Simmer for 15 minutes until chicken reaches 165°F internally and squash becomes fork-tender but not mushy. The vegetables should maintain their shape while the broth becomes infused with autumn spices.
Stir in chopped fresh kale and cook 2-3 minutes just until the leaves wilt and turn bright green. Taste and adjust seasoning with salt and pepper to your preference.
Remove from heat and ladle into bowls immediately. Garnish each serving with fresh parsley and serve with crusty bread or oyster crackers for textural contrast.