Cook pasta according to packaging instructions.
While water is boiling and pasta is cooking, sauté onions in a heavy bottom skillet with olive oil, salt, and pepper on medium heat.
When onions are starting to brown, add sun-dried tomatoes and continue to cook until onions are caramelized.
Turn heat down to medium-low and add in the white wine. Scrape any bits off the bottom of the pot.
Add milk, goat cheese, and spinach and mix to combine. Ensure that all of the goat cheese has been thoroughly mixed into the sauce.
When sauce elements are combined, add in the cooked pasta and stir gently. If sauce needs loosening up, add some pasta water.
(optional) Stir in parmesan.
Taste pasta for seasonings and add extra salt and pepper as needed.
Serve pasta and add any other toppings like toasted walnuts, breadcrumbs, or red pepper flakes.