Directions

• Preheat the oven to 400 degrees Fahrenheit. Grease a 10 inch tart pan with removable bottom.
• Roll out the puff pastry between plastic wrap, to form a 13 inch circle, approximately. Remove one side of the plastic wrap, and drape the puff pastry over the pan, gently pressing it into the corners. If the dough seems too warm, refrigerate before removing the other side of the plastic wrap. After removing all the plastic wrap, place in the fridge while waiting to be filled.
• In the meanwhile, place the sliced mushrooms in a non stick medium skillet, with 1/4 cup of water. This is a trick that I learned from America Test Kitchen and it does wonders when cooking mushrooms. Place the skillet on medium heat and stir a few times, until all the water is absorbed. Then add the butter, 1/4 teaspoon of salt, and thyme. Cook for 4 to 5 minutes, until the mushrooms are lightly golden. Set aside to cool.
• In a medium bowl, whisk the eggs, milk, the remaining 1/2 teaspoon of salt, pepper, and 1 1/2 cups of cheese – you will spread 1/2 cup on the bottom of the tart. Mix until well combined, then add the cooled mushrooms
• Take the tart crust out of the fridge – the dough will be stiff. Sprinkle the remaining 1/2 cup of cheese on the bottom, then pour the filling, making sure that mushrooms and cheese are evenly distributed. The dough should be easier to handle now. Fold the overhang inward, and make sure to partially go over the filling.
• Wrap aluminum foil around the pan – the butter from the puff pastry may leak, as well as the filling if there are little holes. Bake for 30 to 35 minutes, until golden brown, and the filling jiggles only slightly.
• Place on a cooling rack to cool, and wait to unmold until at room temperature.