VEGGIES: In a large pot over medium heat, melt 1 tablespoon of the butter and add 1 tablespoon olive oil. Add the diced onion, carrots, celery, and bell pepper and saute 7-9 minutes. Add garlic and saute 30 seconds more.
TORTELLINI: In a separate pot, follow package directions to cook tortellini. Drain and set aside. (Don't forget to salt the pasta water when cooking the tortellini; I add in 1 teaspoon salt to every 4 cups of water.)
SEASONINGS: To the pot with the veggies, add in the seasonings -- dried thyme, dried oregano, Italian seasoning, and cayenne pepper (if using). Season to taste with salt and pepper; I add 1 teaspoon salt and 1/2 teaspoon pepper, but add to personal preference. Stir seasonings for 30 seconds.
THICKEN: Increase the heat to medium high. Push veggies to the sides of the pot and add the remaining 4 tablespoon butter to the center and stir until melted. Once melted, sprinkle in the flour. Briskly mix to incorporate the flour and then stir for 1 minute to cook off the raw flavor of the flour. Gradually whisk in 1 cup of chicken broth until it starts to thicken (~1 minute); then add the remaining chicken broth. Whisk until it thickens (~2-3 minutes) and then gradually add in the milk continuing to stir constantly. Slightly reduce the heat, cook stirring constantly, until mixture begins to gently boil and thicken (another ~2-5 minutes).
CORN & CHICKEN: Reduce heat to medium low. Add in the frozen corn and rotisserie chicken. Stir to warm through. (If the soup has thickened too much, add in some additional chicken stock; I usually add up to 1/2 cup to 1 cup extra).
CHEESE AND SERVING: Remove pot from heat and add in the cheese. Stir to melt. Season soup to taste with any additional salt and pepper. Add in parsley (if using). Serve, adding tortellini to individual bowls. Garnish with fresh thyme and serve with crusty bread if desired.