Preheat your oven to 350°F (175°C).

In a large skillet, heat olive oil over medium heat for about 2 minutes, add the ground beef and cook for 5-7 minutes until browned, season with salt and pepper, then remove from heat.

In the same skillet, sauté diced onions and sliced mushrooms for 5-7 minutes until tender, then add minced garlic and stir for another minute.

Combine the browned beef with sautéed vegetables, stir in Worcestershire sauce, soy sauce, Dijon mustard, and beef broth. Let simmer for 5 minutes, then fold in sour cream.

Cube hamburger buns and layer in casserole dish, pour beef and mushroom mixture over bread cubes.

Sprinkle shredded Swiss cheese over the casserole.

Bake in the preheated oven for 25-30 minutes until cheese is melty and golden brown.

Remove from oven, let cool for a few minutes, and garnish with chopped parsley.