Mushroom Onion Quiche

I bought some frozen pastry shells and wanted to make some breakfast for dinner. I found a recipe to use as an example. I partially baked the defrosted pie crust before filling it, but I think I should have put some weights in it because that caused it to crack. Then when I baked the filling, part of it seeped through the cracks and made those parts of the crust soggy. Although the filling tasted pretty good, it was better the second day, so it would have probably helped to let it cool to room temperature before eating. I also can't remember what cheese I used. I want to say it was gruyere. I just served it with some green salad.

Ingredients:
1 thawed frozen pie crust
1 bag chopped mushrooms
1 red onion, sliced
3 eggs
milk
salt, pepper
butter
brown sugar
shredded cheese

Directions:

Thaw the pie crust, poke holes in it with a fork and blind bake for about 10 minutes at 350. Meanwhile, sautee the onions in butter over medium heat. Add brown sugar, and cook until softened before adding mushrooms until cooked through. Season with salt and pepper. Add mushroom onion mixture to the pie crust and top with shredded cheese. Beat the eggs with milk, season with salt and pepper and pour into the pie crust over mushroom mixture. Bake for about 20 minutes at 375. Add some cheese and broil before taking it out of the oven. Let it cool at least 10 minutes before cutting. Top with some chopped parsley.