Preheat the oven to 350°F, and preheat a skillet on the stove over medium heat.
Thinly slice the mushrooms.
Sauté sliced mushrooms in a pan with 2 tablespoons of butter over medium heat for 5 minutes.
Reduce the heat to low and cook until reduced and lightly browned, about 10 minutes.
Slice the top of the rind off of the brie, leaving the bottom and sides intact.
Spread out a sheet of defrosted puff pastry and place the brie in the center with the cut side up.
Pour half of the lemon curd on top of the brie.
Fold the top and bottom of the sheet of puff pastry over the brie.
Then fold in the sides leaving a little bit open in the center.
Seal the folds of puff pastry together with a brush of water.
Bake in a preheated 350°F oven for 45 minutes, or until browned.
Carefully transfer to the serving plate, top with the sautéed mushrooms and remaining lemon curd and enjoy!