Heat 1 to 2 tablespoons of olive oil in a large pot over medium heat.

Add the chopped onion, minced garlic, sliced carrots, and sliced celery. Sauté, stirring occasionally, until the vegetables soften and the onion turns translucent, about 5 to 7 minutes.

Push the vegetables to the side of the pot. Add the diced chicken in a single layer and cook until the pieces lose their pink edges, about 4 to 6 minutes. Stir so the chicken cooks evenly.

Pour in 4 cups of chicken broth and bring the pot up to a gentle simmer.

Sprinkle in the thyme, crushed rosemary, and a pinch of salt and pepper. Simmer gently so the flavors meld. Taste as it cooks and adjust seasoning later.

Stir in the spinach or kale. Continue simmering for 10 minutes until the greens are tender and the soup is heated through.

Taste and adjust salt and pepper if needed. Serve warm.