In a Dutch oven heat the olive oil on medium high and add the chicken. Cook the chicken until golden brown on both sides and cooked through the center to 165 degrees, about 8 to 10 minutes depending on the thickness of the piece of chicken.

Remove the chicken from the pot and place on a plate to rest.

Add the garlic to the pot and toss. Do not burn!

Add the butter to the pot stirring constantly until the butter melts. Add the flour, salt and pepper. Whisk the flour into the butter until a thick roux forms.

Cook about 3 minutes while whisking until lump free, thick and creamy. Be sure to scrape the bottom of the pot and along the edges well so the thick rue has dissolved. Bring to a boil until thickened.

Slowly add the milk, half and half, or heavy whipping cream to the pot whisking constantly until the liquids have combined and the sauce is thick and creamy.

Add the shredded parmesan cheese ¼ cup at a time while whisking until each addition has melted into the broth.

Once the cheese has melted into the broth whisk the chicken broth into the pot and bring to a boil, occasionally whisking. While waiting for it to come to a boil shred the chicken into bite size pieces.

Next, add the tortellini, shredded chicken, spinach if using, and red pepper flakes to the pot. Stir to combine. Bring the pot to a simmer and cook until all ingredients are piping hot.