Heat a heavy bottomed skillet. Add 2 Tbsp. butter and 1 Tbsp. olive oil. Heat until bubbling.
Add the shallot and saute until transparent. Do not brown.
Add garlic. Mix well and continue cooking for a couple of minutes.
Add the mushrooms and mix thoroughly so they are completely coated in the butter and olive oil. Add a little more butter if they look too dry.
Add herbs and seasoning and simmer until the mushrooms are softened. Taste and adjust with more seasoning if necessary.
Add just enough chicken broth to cover the mixture. Continue simmering until the liquid is reduced and the mixture is thickened.
Remove from the heat and cool.
Preheat oven to 400 degrees.
Lightly flour a work surface and roll out thawed puff pastry just enough to cover the Brie completely.
Slice the Brie in half horizontally. Lay half of the Brie, cut side up, on top of the pastry.
Place the cooled mushroom mixture on top. Place the second half of Brie, cut side down on top.
Cover the Brie with pastry starting with opposite corners. Decorate the top with a little leaf design. Place the wrapped Brie on a baking sheet lined with parchment paper. Brush top and sides with egg wash.
Refrigerate at least 30 minutes before baking to prevent the cheese from melting too much.
Bake at 400 degrees for 30 minutes or until the pastry is nicely browned.