for the cake:
1 cup sugar
1/4 tsp salt
1/2 tsp vanilla
1 cup flour
for chocolate whipped cream filling:
1 cup heavy cream
2 tbsp powdered sugar
1 tbsp cocoa
teeny tiny pinch of salt
for mocha buttercream:
1 tsp instant coffee
1 tsp boiling water
1 stick butter, softened
3/4 cup powdered sugar
2 tbsp cocoa
for cute little meringue mushrooms:
2 egg whites
1/2 cup sugar
1/4 tsp cream of tartar
Preheat oven to 350.
Beat the egg yolks until very pale and thick. Set aside. In another bowl, whip the egg whites until stiff peaks form. Gradually add sugar, salt and vanilla extract. Fold egg yolks into egg whites and then gently fold in flour. Spread mixture onto a WELL GREASED and LINED (either with a Silpat or parchment paper) jelly roll pan, smoothing it out with a spoon or off-set spatula. Bake for 10-13 minutes, until just slightly starting to turn golden.
Once cake comes out of oven, run a knife along the sides of the jelly roll pan and turn cake out onto a clean dish towel. Do this slowly! Then, wrap up dishtowel and cake together. Let cake cool for 20 minutes wrapped up like this then unwrap cake and lay flat.
While the cake is cooling, whip the cream for the filling and add the cocoa, powdered sugar and salt. Spread whipped cream onto cooled cake, leaving an inch border around all sides. Roll cake up with filling.
Then, make the mocha buttercream. Beat the butter and buttered sugar until very light and fluffy. Add cocoa. Mix together the instant coffee and boiling water and add to frosting. Continue beating on high speed for another ten minutes until VERY VERY FLUFFY AND LIGHT (you can't over-beat this...keep going).
Spread frosting all over the top and sides of the cake roll. Place in refrigerator while you make the mushrooms.
To make the mushrooms (these are optional but super cute and fun), whip the egg whites with the sugar and cream of tartar until stiff, glossy peaks form. Pipe out of a pastry bag or plastic bag into 10 little mounds on a lined baking sheet. Then, pipe 10 little "stems" to go with the mounds (just a thick short line of meringue). Save one tablespoon of meringue and place in fridge. Bake mushroom caps and stems at 200 degrees for 1.5 hours, until very light and perfectly crisp.
Remove from oven and "glue" mushroom caps and stems together with your leftover meringue. Carefully place mushrooms back on the baking sheet and resume baking for another 30-45 minutes until "glue" has baked. Let mushrooms cool before using.
To assemble and serve the buche de noel, cut a slice of the cake roll and place on a plate that you already sifted with cocoa powder. Sift cocoa powder on two meringue mushrooms and place mushrooms next to or on top of cake roll. Serve.
all day long
**Great Grandma says "the mocha butter frosting is a delicious icing that could be used on other cakes" <-----I concur
** buche de noel can be stored wrapped in plastic wrap
in the fridge for up to three days. Meringue mushrooms can be stored
wrapped in plastic wrap at room temperature