In a large pot or dutch oven, add the olive oil, diced sweet potato, garlic, and onion.
Saute the vegetables over 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 it to a boil.
Boil the pasta for 10-11 minutes, stirring often (turn down the heat if the boil is too strong).
Once the pasta has finished cooking, 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 the sauce starts to thicken (3-6 minutes).
Add the chopped spinach and wilt it for 1-2 minutes, stirring frequently.
Serve your sweet potato pasta garnished with additional parmesan cheese, if desired.