Preheat your oven to 350°F (175°C).
Thinly slice the cabbage and onions.
In a large skillet, melt the butter over medium heat.
Add the sliced onions and cabbage to the skillet, cooking until they begin to soften.
Pour in the beef broth and Worcestershire sauce, then season with salt, pepper, garlic powder, and thyme.
Stir everything together and let it simmer for a few minutes.
Transfer the mixture to a baking dish and top it with croutons and shredded Gruyere cheese.
Bake in the preheated oven for about 25-30 minutes, or until the cheese is melted and bubbly.
