Slice the onions

• Peel and thinly slice the yellow onions.

Caramelize the onions

• Melt the butter with the olive oil in a large pot.
• Add the onions and cook low and slow, stirring occasionally, until deeply golden.

Shred the cheese

• Meanwhile, grate the Gruyère and Parmesan and combine them.

Add aromatics and deglaze

• Stir the garlic, fresh thyme, nutmeg and black pepper into the onions.
• Pour in the white wine and Worcestershire sauce and scrape the bottom of the pot.

Simmer the pasta

• Add the pasta and the beef stock.
• Simmer until the pasta is cooked and the liquid has reduced.

Finish with cream and cheese

• Lower the heat and stir in the heavy cream.
• Add the grated cheeses and mix until melted and creamy.

Serve

• Plate the pasta and top with extra thyme, Parmesan and a drizzle of Calabrian chili oil.