In a large skillet, heat the olive oil over medium heat. Toss in the thinly sliced onions and a sprinkle of salt. Sauté for about 15-20 minutes until they turn golden brown and fragrant.

Once the onions are caramelized, add the minced garlic and dried thyme. Stir for about a minute until the garlic is fragrant.

Pour in the beef broth and let it simmer for 5 minutes. Then stir in the heavy cream followed by a good pinch of salt and pepper.

Add the gnocchi into the skillet, stirring gently to coat them in the cream mixture. Allow everything to cook together for another 5-7 minutes until the gnocchi are soft.

Sprinkle in the Gruyère and mozzarella cheeses, stirring until they are melted and incorporated.

Transfer the gnocchi mixture into a lightly greased baking dish. Top it off with a little extra cheese. Bake it in a preheated oven at 375°F (190°C) for about 20 minutes, or until the top is golden and bubbly.

Once baked, garnish with fresh parsley and serve hot.