Dice onion and garlic, and slice the mushroomsSauté onions in 2 teaspoons of olive oil in a skillet over medium heat. Once translucentthen add the garlic and cook down together
Add the sliced mushrooms and sauté on high heat. Once mushrooms are starting to brown, add an extra teaspoon of olive oil and season with salt and pepperRemove off the heat and allow mixture to cool at room temperature
Thaw puff pastry sheet and place on a baking tray with a baking sheet. Lightly score a square 1 inch border around the puff pastry sheet, making sure not to cut all the way through. Using a fork, poke a few holes in the middle of the pastry
Add the grated cheese to the middle of the pastry and top with the sautéed mushrooms. Spray the border with olive oil spray, or alternatively brush the border with egg wash
Bake for 15-20 mins until golden brown. Top with chopped parsley, cut into 4 squares and enjoy your crispy Mushroom Tart!