In a large skillet, heat 2 tablespoons of olive oil and 2 tablespoons of salted butter over medium heat. Add 2 pounds of sliced yellow onions and season with a pinch of kosher salt. Cook for 45–60 minutes, stirring occasionally, until the onions become deep caramel brown and are beautifully fragrant.

In the final 5 minutes of cooking, stir in 6 minced garlic cloves and 1.5 tablespoons of fresh thyme. Sauté until fragrant, stirring regularly to prevent burning.

Pour 0.5 cup of dry white wine into the skillet, scraping up any browned bits. Allow the wine to reduce for 3-4 minutes until most of the liquid has evaporated.

Sprinkle in 2.5 tablespoons of all-purpose flour, cooking for about 1 minute while stirring constantly. Gradually whisk in 2.5 cups of low sodium beef stock, along with 2.5 teaspoons of Dijon mustard and 1 teaspoon of Worcestershire sauce. Add 1 bay leaf, bringing to a gentle boil for about 2 minutes until thickened.

Reduce the heat and let the sauce simmer for 6-7 minutes. Taste and adjust seasoning with kosher salt and freshly cracked black pepper.

In a separate pot, bring salted water to a rolling boil. Add 24 ounces of gnocchi, cooking until they float to the top, about 2-3 minutes. Drain the gnocchi and fold them into the simmering sauce.

Mix in 1.5 cups of freshly grated Gruyère cheese and 0.5 cup of freshly grated Parmesan cheese. Stir until the cheese is slightly melted and evenly distributed.

Transfer the gnocchi mixture into a baking dish and place under the broiler. Broil for 3-5 minutes until the cheese is bubbly and golden brown.

Once out of the oven, discard the bay leaf and serve hot. Garnish with a sprinkle of fresh thyme if desired.