Preheat the oven to 400 degrees F.
In a skillet, melt the butter over medium-high heat. Add the shallots and garlic and cook, stirring, until soft and fragrant, 1 to 2 minutes. Add the mushrooms and cook until they give off their liquid and start to color, about 4 minutes. Add the crabmeat, Essence, salt, and cayenne and cook, stirring, for 1 minute. Add the green onions and parsley and cook for 1 minute. Remove from the heat and stir in the truffle oil. Let cool and fold in the goat cheese. Adjust the seasoning to taste.
Roll out each sheet of pastry slightly, and cut each piece into a round 1-inch larger than the Brie. Using a paring knife, cut several leaves or other decorative shapes from the pastry scraps. Place 1 piece of pastry on a baking sheet lined with parchment paper.
Cut the Brie in 1/2 horizontally and lay 1 piece in the center of the pastry sheet, cut side up. Spread the cooled crabmeat mixture over the cut Brie and top with the remaining Brie 1/2, gently pushing the 2 halves together.
Paint the edges of the bottom piece of pastry with the egg wash. Top the cheese with the remaining pastry sheet, pinching the edges together to seal. Paint the top pastry lightly with the egg wash, being careful not to let any drip down the sides. Arrange the decorative leaves on top, and lightly paint with egg wash. Bake until the pastry is puffed and golden brown, about 20 minutes. Remove from the oven.
Line a platter with the watercress and place the baked brie on top. Let sit for 5 minutes. Surround with toast points and serve.
Yield: 6 to 8 servings