Heat the oven to 400'F. Beat the egg and water together in a small bowl, set aside. You will need this to seal the pastries and then brush on the pastries.
Take the puff pastry out of the package and let it thaw for about 40 minutes.
Thaw the spinach and then wring it out in a tea towel. Remove and put into a bowl.
In a med. size saute pan, add the coconut oil and saute the onions for a couple of minutes. Then add the mushrooms and garlic and saute for a few more minutes. Add the spinach and the frozen corn and saute until the liquid is all absorbed.
Turn off the heat, add the cheese and mix it into the vegetables.
Divide the mixture in two equal parts.
When the pastry is thawed roll it into a 12x12 inch square. Cut into 6 pieces.
Put an equal amount of the filling from one half of the veggies on each of the 6 squares. Brush 1/2 of the pastry with the egg/water wash, fold over, seal and place on a lined baking sheet. Repeat this with the other sheet of puff pastry.
Bake for 15 minutes or until golden brown. Remove from the oven and set on a metal baking rack to cool.