Preheat the oven according to the puff pastry package directions.
Pinch together the seams and roll out the pastry into a rectangle slightly smaller than your baking sheet. Leaving a margin of about 1/2 inch around the edge, pierce the center of the pastry with a fork in several places.
If time permits, put the pastry on a parchment-lined baking sheet and place it in the freezer for a few minutes to allow the butter to firm up. This helps keep the butter from melting too quickly and creating lopsided pastry.
Sauté the mushrooms in olive oil over medium-low heat until they are dark in color and the excess moisture has evaporated.
As the mushrooms cook, add the goat cheese, salt and pepper to a mixing bowl and whip with a stand or hand mixer until the cheese is airy and spreadable. If desired, add a little of the cream or milk to help achieve a whipped consistency.
Take the pastry out of the freezer. Spread the whipped goat cheese over it, taking care to leave the border.
Evenly spread the warm mushroom mixture over the goat cheese and sprinkle with the basil and the crumbled goat cheese.
Bake until golden brown. Serve.