1 1/3 ounces (40 grams) unsalted butter, room temperature
To Assemble the Logs
Confectioners' sugar, for work surface and serving
1 pound marzipan
7 ounces chopped pistachios
<u>Marzipan Holly</u>, for decorating (optional)
<u>Meringue Mushrooms</u>, for decorating (optional)
Make the ganache: Place the gianduja in a medium heatproof bowl; set aside. In a small saucepan, combine cream and sugar over medium-high heat; bring to a boil. Strain the cream mixture through a fine sieve over the gianduja. Add butter, and stir until smooth. Cover with plastic wrap, and let stand in a cool place (not the refrigerator) until firm, about 8 hours.
Dust the work surface, rolling pin, and marzipan lightly with confectioners' sugar to keep it from sticking. Roll marzipan into a 6-by-21-inch rectangle, about 1/8-inch-thick. Trim edges, and cut into three 6-by-7-inch rectangles.
Remove excess sugar from marzipan with a pastry brush. Spread each marzipan rectangle with 4 tablespoons of the ganache. Sprinkle with 1/3 of the chopped pistachios. Roll tightly into a log enclosing pistachios. Place on a baking sheet and refrigerate or freeze for 1 hour.
Melt remaining ganache in a heatproof bowl set over a pan of simmering water. Dip the marzipan logs in the ganache, turning to coat. Using a paring knife, trim the ends of each roll, cutting on the bias; reserve ends. Use the tines of a fork to create wood-grain design on each log.
Place ends, cut-side up, on the logs, forming branches. Decorate with marzipan holly leaves and berries. Will keep refrigerated for up to 3 days. Just before serving, dust with confectioners' sugar.