This recipe substitutes 1/3 c. of the cake flour with dutch process cocoa powder; substitutes David Leibovitz' original ricotta filling with a lighter version of Francois Payard's green tea pastry cream; and lightens the sugar load in every component. The green tea in the pastry cream and the serotonin in the dark chocolate can only contribute to the good will of the holidays. If you are pressed for time, garnish with crushed pistachios and strained pomegranate seeds and sift confectioners' sugar on top. If you opt for the meringue mushrooms, make them a day ahead. (They take 1-1/2 hours to bake and another hour to cool down.) Store them in an air-tight container and add them as garnish at the last minute to maintain crispness. See Notes below for additional garnish ideas or Google "Buche de Noel" followed by the year for more extravagant inspiration from France's best patisseries.