Cook pasta according to package directions. Peel and finely chop garlic. Chop chicken into bite-size cubes.
Heat the olive oil in a large skillet and add chicken. Season with 1/4 teaspoon salt and pepper and cook 5-8 minutes, or until no longer pink.
Remove the chicken from the pan and set aside.
In the same pan, add the garlic and sauté for one minute over medium heat.
Sprinkle the flour over the garlic and slowly add in the chicken stock. Stir constantly with a whisk to avoid lumps.
Add in the skim milk and remaining 1/4 teaspoon salt, stir, and allow to reach a simmer to thicken sauce.
Once the sauce is thickened, add in the spinach and stir until wilted.
Remove from heat and add in the cooked penne, chicken and Parmesan cheese. Stir to coat.