Cook pasta according to package directions. While pasta is cooking, mash up sweet potatoes. Reserve 1 cup of pasta water.
In a medium saucepan, saute garlic, herbs, and olive oil over a medium heat.
Once garlic is fragrant, lower the heat and add sweet potatoes. Slowly add enough pasta water to make the mixture smooth and easy to mix.
Combine the sauce and pasta. Serve immediately with parmesan cheese if desired.