Walnut Orange Buche de Noel
Cake Roll
  1. Preheat oven to 300 F. Line a 12 X 17-inch rimmed baking sheet with parchment paper. Spray & flour parchment, tapping off excess; set aside. In a food processor, pulse walnuts with flour until coarsely ground; set aside.
  2. In the bowl of an electric mixer, whisk egg yolks with 5 Tbsp sugar until thick & pale. Beat in vanilla. In a clean mixing bowl fitted with a clean whisk, beat egg whites with salt until soft peaks. form. Gradually add remaining 5 Tbsp sugar, beating until stiff, glossy peaks form. Fold egg whites into yolk mixture in 3 equal batches; add walnut/flour mixture with last batch.
  3. Spread batter evenly in prepared baking pan. Bake until top is golden & springs back when touched, about 30 minutes. Run a small sharp knife around edges of cake; invert cake onto a clean, dry towel dusted with powdered sugar. Peel off parchment paper. Starting at short side, gently roll the cake into a log, incorporating towel. Transfer to a wire rack, cool completely for about 1 hour.
Orange Mascarpone Filling
  1. In a bowl of an electric mixer fitted with a paddle attachment, beat all ingredients except heavy cream, until smooth. Gently fold in whipped cream.
Chocolate Bark
  1. Line a baking sheet with parchment paper; set aside. Place chocolate in a small heat-proof bowl; set over a pan of simmering water, stir until melted. Remove bowl from heat; let chocolate cool, stirring occasionally, until it registers 88 degrees on a candy thermometer.
  2. Pour onto prepared baking sheet; spread evenly with an offset spatula. Refrigerate until firm but still pliable, 8-10 minutes. Tear into jagged pieces, no larger than 1 1/2-inches each. Refrigerate until firm, about 15 minutes.
Meringue Mushrooms
  1. Preheat oven to 200 F. Line 2 baking sheets with parchment paper. In a bowl, beat egg whites until frothy; add cream of tartar. Continue beating until soft peaks form then increase speed to high & gradually add sugar, 1 tsp at a time. Beat egg whites until shiny & hold stiff peaks, being careful not to dry. Spoon meringue into a large pastry bag fitted with a 1/2-inch round tip.
  2. For Mushroom Caps: hold the pastry bag at a 90 degree angle about 1/2-inch from the parchment. Using firm & even pressure, squeeze out a round meringue disk about 2-inches in diameter & 1-inch high. Stop squeezing, then twist the bag & lift it from the meringue to get a clean ‘break’ from the cap. Repeat in regular intervals on the baking sheet until you have approximately 2 dozen mushroom caps. You can smooth out the tops by wetting you index finger & lightly running it along the caps.
  3. For Stems: Position the bag perpendicular, about 1/2-inch from the baking sheet. Begin squeezing the bag to form a 1-inch round base. Continue to squeeze as you slowly & evenly draw the bag up, forming a tapering stem about 1 1/2-inches tall. Use the remaining meringue to pipe as many stems as possible.
  4. Bake the meringues for about 90 minutes, turning them halfway through the cooking time to ensure even baking. The meringues should be hard to the touch & easy to lift off the parchment. Once they are done, turn off the oven & let them sit in the oven for several hours.
  5. To Assemble the Mushrooms: melt white chocolate in a small bowl in the microwave, stirring after every 30 seconds to prevent overheating. Use a toothpick to carve a small hole in the bottom of a mushroom cap. Dip the top of a stem into white chocolate, then place the stem in the hole on the bottom of mushroom cap. Repeat until all caps & stems are used; placing them on a baking sheet. Place cocoa powder in a wire sieve & lightly dust tops of the mushrooms.
  6. Due to the amount of time required to make mushrooms, it is nice if you can do this well in advance. Mushrooms can be stored for up to a month in an airtight container in a cool, dark room. Humidity can make them collapse, so do not place them on a cake (or in the refrigerator) until immediately before serving.
Assembly of Buche de Noel
  1. Reserve 1 1/2 cups mascarpone filling. Unroll cake & spread with remaining filling, leaving a 1/2-inch border on all sides. Carefully re-roll cake. Arrange, seam side down, on serving platter. Spread top & sides ONLY with remaining 1 1/2 cups mascarpone filling. Using a serrated knife, trim off ends of log to even it ( if you wish ). Arrange chocolate bark, overlapping pieces slightly, to look like wood bark. Refrigerate until firm, at least 1 hour. Garnish with meringue mushrooms, fresh, whole cranberries, marzipan holly leaves, a dusting of powdered sugar or whatever is your choice.