Heat a large pot over medium heat and add the olive oil and butter. Once the butter melts, add in the onion, carrots, celery, garlic, oregano, salt and pepper. Stir and cook until the veggies soften, about 5 to 6 minutes. Stir in the shredded chicken and cook for a minute or two. Add in the chicken stock and bring the mixture to a boil, then reduce it to a simmer. Add in the tortellini and cook it for 5 minutes.

While the tortellini is cooking, fill a shaker cup with the milk. Add the flour to the milk and shake the cup for at least 30 seconds. After 5 minutes, stream in the milk slurry while stirring. Bring the soup back to a simmer and let it simmer for 10 or 15 minutes as it thickens.

Taste it and season more with salt and pepper if you find it necessary. Sprinkle with fresh oregano and thyme and serve!