1Heat olive oil in a large saute pan. Add onions stirring continuously until they start to soften. Add mushrooms, salt and pepper. Stir till mushrooms release their liquid.
2Add wine and cook until almost all evaporate. Remove from heat and set aside.
3Preheat oven to 350℉
4Line a baking sheet with parchment paper.
Unfold defrosted pastry sheets. Lay them side by side (along the long side) and press to seal.
With a sharp knife score 1/2 inch border around pastry(don't cut all the way) Lift the sides.
5Spread mushroom mixture on pastry. Top with gruyére cheese.