In a large pot or dutch oven, add the olive oil, diced sweet potato, garlic, and onion
Saute on medium high heat for 8-10 minutes, or until the sweet potatoes start to soften
Add the penne pasta , sage, thyme, and vegetable broth and bring to a boil
boil for 10-11 minutes, stirring often (turn down the heat if the boil is too strong)
Turn the heat down to low and add the parmesan cheese, heavy whipping cream, and salt and pepper to taste (I used 1/2 teaspoon each)
Continue stirring until sauce starts to thicken (3-6 minutes)
Add spinach and wilt for 1-2 minutes, stirring frequently
Serve garnished with additional parmesan cheese, if desired