1Place two tablespoons of butter in pan. Saute the onion, mushrooms, and garlic until softened. Add the beef cook until no longer pink. Stir in the steak sauce, herbs, salt and pepper. Set aside.
2Place the other 2 tbsp. butter in sauce pan. Stir in the flour and make a roux. Slowly stir in the milk and cook until thickened. Add the mustard and ham. Stir the meat mixture and mustard mixture together.
3Grease a 9 x 13 pan. Lay the hash browns in the bottom of pan. Pour the meat mixture over top. Scatter the white cheddar cheese cubes on the top and press into the casserole. Top with shredded swiss cheese.
4Bake at 350 degrees for 25 to 30 minutes.
Garnish with dried chives