Heat olive oil in a large pot over medium heat, then sauté onion, carrots, and celery until softened, about 5 minutes, stirring occasionally as they turn glossy.

Add garlic and dried thyme and cook for 1 minute until fragrant.

Add chicken broth and chicken to the pot, then simmer for 18 minutes until the chicken is cooked through and flakes easily.

Remove the chicken, shred it, and return the shredded chicken to the pot.

Stir in the orzo and simmer for 8-9 minutes until tender, looking for the pasta to soften while the broth gently bubbles.

For avgolemono style, whisk eggs with lemon juice, then slowly ladle a bit of the hot broth into the eggs while whisking to temper, and stir the mixture back into the pot until the soup looks slightly thickened and silky.

For regular style, simply stir in lemon juice and lemon zest to brighten the broth.

Add baby spinach and cook until wilted, about 1-2 minutes, then stir in fresh dill.

Season with salt and black pepper to taste, then stir until evenly distributed and the flavor is balanced.