Heat a large saute pan over medium-low heat. Saute the bacon until it fully renders and is slightly crispy. Remove the bacon from the pan and place it in a small bowl for pie assembly time later. Leave all the bacon grease in the pan and leave the heat on.

Add the onions to the pan of bacon grease and saute until tender. Now add the mushrooms. Saute for about 5 minutes until the mushrooms are tender. Pour in the cream, sprinkle on the dill weed, salt, and pepper, and stir it up. Let the mixture simmer for about 10 minutes to get the flavors melding and reduce a bit. Stir it occasionally. Finally, add the Swiss cheese and stir it in. Just when it’s melted, remove the pan from the heat.

Find a 9x13 pan that you don’t mind cutting in and spray it with Pam. Sprinkle a little flour onto your work surface, place one of the puff pastry sheets on the flour, sprinkle a little more flour on top so your rolling pin doesn’t stick, and gently roll it out to about the size of the 9x13 pan. You can err on going slightly bigger. Place the sheet in the bottom of the pan and press it out to the sides to fill the bottom. You can roll it up the sides of the pan a little if there’s extra slack.

Sprinkle on the Parmesan cheese evenly across the dough. Now dump the mushroom and cream mixture over the dough and spread it out evenly to the sides of the pan. Sprinkle the bacon bits across the top of that. Roll out the second sheet of puff pastry like the first and place it on top of the pie filling. Work it to the sides the best you can and tuck it down the sides. With a knife, make a few diagonal slices across the top to allow steam to escape. Brush the top with the beaten egg.