Prep the chicken: Cube and season the chicken breast with salt and pepper.
Cook the chicken: In a large pot, heat 1 teaspoon of olive oil over medium heat. Add the chicken breast and cook until browned on both sides and cooked through, about 6-7 minutes per side.
Add the veggies: In the same pot, add the remaining teaspoon of olive oil. Add the diced onion, grated carrot, spinach and diced celery. Sauté until the vegetables are tender, about 5-7 minutes. Add the minced garlic and cook for an additional minute until fragrant.
Simmer: Pour in the chicken broth and bring to a boil. Add the gnocchi to the boiling broth. Cook according to the package instructions, usually about 3-4 minutes, until the gnocchi floats to the top. Reduce the heat to medium and add dried thyme.
Make a slurry: In a small bowl, whisk the cornstarch with a few tablespoons of cold water until smooth. Gradually stir the cornstarch mixture into the soup.
Thicken the soup: Add the skim milk, stirring constantly. Simmer the soup for about 5-10 minutes until it thickens to your desired consistency. Adjust seasoning with more salt and pepper if needed. Ladle the soup into bowls and serve hot.