In a large pot, heat the olive oil over medium heat. Add diced sweet potatoes and sauté for about 5-6 minutes until they start to soften and brown slightly.
Stir in the minced garlic and cook for an additional 1 minute until fragrant. Add pasta to the pot with the sweet potatoes, then pour in the broth and the milk, ensuring that the pasta is mostly submerged in the liquid.
Bring the mixture to a simmer over medium heat; stir occasionally to prevent pasta from sticking to the pot.
Once the pasta is about halfway cooked (around 5-7 minutes), add crumbled goat cheese, and sage to the pot; stir well.
Continue to simmer and stir until the pasta is cooked, and the sweet potatoes are tender. The liquid should be mostly absorbed, leaving a creamy sauce.
Season the pasta with salt and black pepper to taste. Remember that the goat cheese adds some saltiness, so adjust accordingly. Remove the pot from the heat.
Serve the individual plates or bowls. Sprinkle some grated Parmesan cheese over each serving.
