Preheat oven to 375 F degrees.
Roll out the puff pastry a bit, so that it's about 18 inches x 14 inches. You'll need about 4 inches down the center of the pastry, so start cutting 1 inch strips, leaving the 4 inches in the center.
Add a tablespoon of butter to a skillet and melt it. Add the mushrooms and kielbasa and fry for a couple minutes. In the meantime, whisk together 6 eggs and mix with the shredded Swiss cheese.Add the eggs to the skillet and cook. Add the parsley for color and season with salt and pepper.
Let the scrambled eggs cool. Place the scrambled eggs in the center of the pastry.
Take a strip from each side and fold over the eggs. One from each side at a time, sort of forming this braid.
Brush the pastry with the egg wash and bake in the oven for about half hour or until nice and golden brown.