Caramelize Onions: In a large skillet, heat 2 tablespoons of olive oil and 1 tablespoon of butter over medium heat. Add 3 sliced yellow onions, stirring to coat them in the oil. Cook for 45-60 minutes, stirring occasionally, until they turn deep brown and caramelized.

Add Aromatics: Stir in 2 teaspoons of fresh thyme and 3 cloves of minced garlic. Cook for another 2 minutes until fragrant.

Create Sauce: Pour in ½ cup of white wine, scrape up the browned bits, and let it simmer for 3 minutes. Add 2 tablespoons of flour, 1 tablespoon of Dijon mustard, and 1 teaspoon of Worcestershire sauce, stirring until thick.

Finish Sauce: Slowly add 2 cups of beef stock and toss in a bay leaf. Simmer for 6-7 minutes, and season with salt and pepper to taste.

Cook Gnocchi: Boil salted water, add 1 pound of gnocchi and cook until they float (about 2 minutes). Drain and fold into the sauce.

Bake: Preheat broiler. Transfer gnocchi mixture to an oven-safe dish, top with ½ cup of Parmesan and 1 cup of Gruyère cheese. Broil for 4-5 minutes until cheese is golden brown.

Garnish & Serve: Let rest for a couple of minutes, garnish with fresh thyme, and serve hot with French bread or salad.