Step 1

Melt butter in a large pot or dutch oven over medium heat. Thinly slice onion and add to dutch oven. Season with a generous pinch of salt. Stir then cover and cook for 5 minutes.

Step 2

Remove lid, turn heat to medium low, and cook until onions are very caramelized. Stir occasionally. This can take 20-45 minutes.

Step 3

Pour in sherry and wine. Deglaze by scraping up the brown bits at the bottom of the pan. Add sprigs of fresh thyme and season to taste with salt and pepper.

Step 4

Add uncooked rigatoni then pour in beef broth and Worcestershire Sauce. Bring to a boil and cook for about 15 minutes or until pasta is al dente.

Step 5

Turn off heat. Discard thyme sprigs. Stir in freshly grated parmesan cheese and half and half until well combined.

Step 6

Serve immediately. Serve with additional parmesan cheese.