Ziti al horno con camote

Ingredients

• 1 box Banza penne
• 2 teaspoons olive oil
• 1 ½ cups diced sweet potato
• 1 small onion, diced
• 1 large garlic clove, minced
• 2 tablespoons flour
• 1 cup low-fat milk
• ½ cup chicken stock
• ½ teaspoon salt
• ¾ cup parmesan cheese, divided
• 2 tablespoons chopped sage, plus more for garnish