For the pear :
125 mL. (1/2 cup) Ginger syrup
75 g. (6 Tbsp.) sugar
1 large pear, halved, peeled and cored
For the ganache :
200 g. (7 oz) dark chocolate pistoles
160 mL. (2/3 cup) heavy cream
3 Tbsp. Ginger syrup
1 Tbsp. unsalted butter
For the cake :
70 g. (1/2 cup) all-purpose flour
20 g. (2 Tbsp.) cocoa powder
4 eggs, separated
67 g. (1/3 cup) sugar
Pinch of salt
For the filling :
150 g. (2/3 cup) mascarpone cheese
125 mL. (1/2 cup) heavy cream
42 g. (1/3 cup) icing sugar
Icing sugar, sugared rosemary and cranberries, to garnish
To poach the pear, combine the syrup and sugar with 250 mL (1 cup) water in a pot just big enough to fit the pear halves in a single layer. Bring to a boil over high heat, add the pear and reduce heat to medium-low. Simmer until tender, about 20 minutes. Allow to cool completely in syrup. Pear can be prepared up to 5 days ahead.
To prepare the ganache, place the chocolate in a medium bowl. Bring the cream and syrup to a boil in a small pot and pour over chocolate. Let sit one minute, then whisk until chocolate is fully melted and mixture is emulsified. Whisk in butter. Cover and allow to cool completely at room temperate.
To make the cake, preheat oven to 350F. Grease a 10” x 15” sheet pan and line with parchment. Sift together flour and cocoa. In a large bowl, whisk egg yolks with sugar until thick and pale. In a separate bowl, whisk egg whites with salt until medium-firm peaks form. Mix in one third of whites to yolk mixture along with flour mixture. Gently fold in remaining whites. Transfer batter to prepared pan, spreading evenly.
Bake for about 10 minutes, until a toothpick inserted in the center comes out clean. Transfer to a wire cooling rack and, using oven mitts, immediately cover pan tightly with foil. Allow to cool completely.
To prepare filling, whip all ingredients until light and fluffy.
To assemble, remove foil from cake pan. Evenly spread the filling over the surface of the cake, leaving a ½” border at one short end. Thinly slice the pear and distribute evenly over the filling. Starting at the end without the border, carefully roll up the cake, peeling back the parchment as you go. Trim both ends with a serrated knife and place the cake seam side down on a serving platter. Frost the cake with ganache, creating a tree bark texture. Lightly dust with icing sugar and decorate with sugared rosemary and cranberries.
The bûche can be made up to two days in advance. Store in the refrigerator and let temper slightly before serving.