Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.

Prepare the filling: in a large, shallow pan over medium-heat, sautee the garlic in the olive oil for a minute, then add the mushrooms, salt and pepper.

Let the mushrooms cook undisturbed for 2-3 minutes allowing them to get color. The less you move them the less liquid that they will release. Once cooked, remove the pan from the heat and stir in the lemon juice, mascarpone cheese, and thyme. Season with salt and pepper. Let cool completely.

When the filling is completely cooled, roll out the pie crusts and cut 20 x 3½ inch (9 cm) circles. Place 10 circles of pie crust on the prepared baking sheet.

Place 2 heaped teaspoons of filling in the center of each circle and brush the edges with the egg wash.

Place the top crusts over the filling and press with your fingers or a fork to seal the edges.

Cut a few slits in the top crust for venting and brush with the remaining egg wash.

Bake for 30-35 minutes, or until the crusts are golden brown. Serve warm or at room temperature.

Store any leftover pies in the refrigerator in an airtight container for up to 3 days. Rewarm in a 300°F (150°C) oven for 15 minutes.