Clean the mushrooms, remove stems, and cut into quarters.

Finely chop the mushrooms and onion.

Heat a skillet over medium heat and melt the butter.

Add the mushroom/onion mix, salt, and thyme to the skillet.

Saute for 5 minutes.

Reduce heat to low and saute for 5 minutes longer, or until most of the moisture has evaporated.

Spoon the mixture into a small bowl and let it cool.

Add lemon juice, mayonnaise, and Worcestershire sauce and mix well to form the spread.

Preheat the oven to 450°F.

Unroll the pie crust on a parchment paper lined baking sheet.

Spread the mushroom filling evenly to within 1 1/2 inches from the edge.

Sprinkle with goat cheese and thyme leaves.

Fold in one edge of the pastry toward the center, covering part of the filling.

Work around the edge, pleating as you go.

Bake for 10 minutes.

Reduce heat to 350°F and bake for 20 to 25 minutes, or until the pastry is golden brown.

Remove from oven and cool pan on wire rack for 10 minutes before serving.