Cut onions in half and then slice into ¼ inch strips. Toss with olive oil, sprig of thyme and a pinch of salt in your pot. Partially cover, and cook over medium heat. Stir every 5 to 10 minutes until onions are soft and have released a lot of liquid.
Remove the cover completely, and continue cooking and stirring until caramelized.
Add in the sherry (or wine), scraping the bottom of the pan to remove all the brown bits.
Slowly, pour in the beef broth and Worchestershire sauce. Bring to a simmer for 10 minutes. Remove the stem from the thyme.
Add the cavatappi to the pot and cover. Cook for 10 minutes or until al dente.
Add in the gruyere, stirring to combine thoroughly.