Preheat your oven to 350°F (175°C) and grease a 9x13-inch casserole dish with butter or cooking spray.

In a large skillet over medium heat, cook 1 pound of ground beef for about 6-8 minutes until browned. Season with salt and pepper to taste, then set aside.

Blend 6 ounces of softened cream cheese in a mixing bowl until smooth, then gradually add 3 eggs, mixing well after each addition.

Incorporate the cooked beef into the cream cheese mixture, stirring thoroughly until well combined.

In the same skillet, melt 2 tablespoons of butter and sauté 5 cups of sliced mushrooms for 5-7 minutes, seasoning with salt, pepper, and dried parsley.

Spoon the beef and cream cheese mixture into the greased dish, spreading it evenly, followed by a layer of sautéed mushrooms. Sprinkle with grated cheese if desired.

Bake the casserole for 20-25 minutes until the top is golden brown and the center is set.

Allow the casserole to rest for about 5-10 minutes before serving to enhance flavors and make slicing easier.