Caramelise the onions

• Melt the butter in a large pan over medium heat.
• Add the sliced onions and salt, then cook on medium-low until deeply caramelised, stirring occasionally.

Deglaze and add aromatics

• Pour in the white wine vinegar and scrape up the browned bits.
• Add the fresh thyme sprigs and stir.

Cook the pasta in the stock

• Add the uncooked pasta, beef stock and Worcestershire sauce.
• Boil until the pasta is cooked and the liquid has reduced to a glossy sauce, stirring regularly.

Finish with cream and Parmesan

• Remove the thyme sprigs.
• Turn off the heat and stir in the cream and grated Parmesan.

Serve

• Plate the pasta and top with extra Parmesan.