in a bowl, combine the ground beef with salt and pepper to taste, water, egg and garlic. At this point you can either brown and drain the meat ahead or you can use it raw. Line the bottom of a 9x13 casserole dish with the meat.
Spread your veggies out over your meat. If canned, drain first. Add mushrooms.
Next layer the entire bag of hashbrowns over the mushrooms. Salt and pepper the potatoes.
Sprinkle the cheese over the potatoes.
Loosely cover the dish with foil and place in a preheated 350 degree oven for 40 mins. If you pre-brown your meat, bake for only 25-30 minutes.
Remove the foil and bake for another 15 minutes until the cheese melts and browns lightly.