Cook the pasta one minute shy of the directions on the box.
Reserve one cup of the pasta water and drain (but do not rinse the pasta).
To a cast iron skillet add the butter and garlic, cooking on medium heat until you can just smell the garlic.
Add in the salt, pepper and flour and whisk well until the flour is fully combined.
Add in the pasta water slowly while whisking.
Add in the greek yogurt slowly while whisking.
Add in the chicken and stir well until coated then add in half of the Parmesan Cheese, whisking until combined.
Add in the pasta and toss it together well with the rest of the ingredients before serving.
Garnish with remaining Parmesan cheese and parsley if desired.