preheat oven to 350

spray 9x13 pan with cooking spray

melt butter in a large pan

saute onion over medium-low heat for 5 mins

add hashbrowns and break apart

saute until soft (about 5 mins)

in a 2nd frying can saute sausage until cooked, drain

in large bowl combine milk, eggs, salt, pepper, nutmeg and mustard

spread highbrown mixture evenly on bottom of pan

evenly add bread cubes

distribute sausage over bread

pour on egg mixture

add parmesan cheese

top with cheddar cheese

bake uncovered for 45-50 mins until puffed and golden brown