These fanciful confections are ideal for the holidays, either served on their own or used to adorn our Birch de Noel.
Heat oven to 200 degrees. Place Swiss meringue in an 18-inch pastry bag fitted with a large 3/4-inch round tip. Line two baking sheets with parchment paper. Pipe meringue, forming domes 1 to 2 inches in diameter. Pipe a stem shape for each dome. Bake for 1 hour; reduce heat to 175 degrees, and continue baking until meringues are completely dry to the touch but not browned, 45 to 60 minutes more.
Fill a medium saucepan one-quarter full with water. Set over medium heat, and bring to a simmer. Place bittersweet chocolate in a heat-proof bowl, and set over simmering water. Turn off heat; stir chocolate occasionally until completely melted. Using an offset spatula, spread bottoms of domed meringues with chocolate; let sit at room temperature.
Place white chocolate in a heat-proof bowl, and set over simmering water. Turn off heat; stir chocolate occasionally until completely melted. Allow to cool slightly. To create mushroom gills, spread white chocolate over dark chocolate; use a toothpick to create lines from the center of the cap's underside to the edges. Let set in a cool, dry place.
Poke a small hole in the center of each mushroom cap using a paring knife. Dip the pointed end of each of the mushroom stems in melted white chocolate, and insert into hole in center of cap. Allow to set. Meringue mushrooms should be kept in an airtight container in a cool, dry place.
The print version of this recipe calls for 3 ounces of white chocolate.