Preheat oven to 425 degrees. Hydrate hashbrowns according to package directions.

Add re-hydrated hashbrowns to a medium bowl and toss with melted butter. Reserve 1 cup of hashbrowns. Press remaining hashbrowns into the bottom and up the sides of a 9 x13 inch baking dish. Bake for about 15 minutes while you prepare the filling, or until hashbrowns are just becoming golden brown.

To make the filling, melt butter in a large skillet over medium heat. Add onion and cook until tender, 3-5 minutes. Stir in flour and cook a minute or two more.

Whisk chicken broth into skillet, then stir in cream. Continue stirring and bring to a simmer to thicken sauce. Stir in chicken, vegetables, thyme, salt and pepper. Simmer for about 5 minutes, or until vegetables are tender. Stir in 1/2 cup of cheddar cheese.

Remove crust from oven. Pour chicken filling over crust. Sprinkle remaining hashbrowns and remaining cheddar cheese over filling. Return to the oven and bake for an additional 20-25 minutes, or until golden brown and bubbling.Before serving, sprinkle with Parmesan cheese and parsley.