1. In a saucepan, heat the heavy cream until just under boiling. Add the chopped chocolate to a small mixing bowl and cover with the hot cream, let stand for 3 minutes and then stir vigorously. The ganâche will be thick, dark and shiny. Chill while making the sponge cake.

2. Grind the pistachios and almonds into flour using a spice or coffee grinder. Shake the grinder well while making the flour and clean it out between batches of nuts.

3. Sift the nut flour mixture using a fine mesh sieve; about 1 ounce of large nut pieces will be left behind.

4. In the bowl of a stand mixer, combine the nut flours, confectioner's sugar and 1/2 of the whole eggs plus 1 egg white mix. Whip on high speed for 8 minutes.

5. Meanwhile, prep the baking sheets. Cover each sheet with parchment paper, leaving a 2-inch overhang on the short ends; this wil help you remove the cakes from the baking sheets. Lightly spray each sheet with non-stick spray, or rub with a little butter.

6. To the bowl of the stand mixer, add in the other 1/2 of the whole egg mix in two batches, scraping down the sides. When all the eggs are incorporated, turn the speed up to high and whip for 10 minutes. The mixture will be thick, light and fluffy.

 7. Preheat the oven to 425F. Remove 1 cup of the batter and fold in the melted butter; reserve separately from the remaining batter.

8. In the cleaned bowl of the stand mixer, make a meringue using the egg whites and sugar. On medium speed, slowly pour the sugar into the egg whites. When all the sugar has been added, turn the speed up to high and whip until soft peaks form, 2 to 3 minutes. Do not overbeat.

9. In the large mixing bowl, fold the meringue into the reserved batter in 3 additions. Do not mix completely before the next addition; white streaks of meringue should be visible when you are done.

10. Gently fold the sifted flour into the batter and meringue in 4 additions, leaving some floury streaks behind.

11. Gently fold in the reserved butter and batter mix, preserving as much fluffy texture as possible.

12. Scoop the batter onto each prepped baking sheet and smooth out into an even layer about 1/4-inch thick. Bake in the 425F oven for 6 to 10 minutes; the cake should be barely brown around the edges and not sticky or shiny. Remove from the oven and immediately take the cakes off the sheet pans using the extra parchment on each end, place on cooling racks and let sit, 5 minutes. Cover each cake with another sheet of parchment paper and flip over; remove the baking paper and cover with a clean, non-terry cloth kitchen towel.

13. Remove the ganâche from the refrigerator and divide in two. Put 1/2 into the cleaned bowl of the stand mixer and and whip on high speed with the softened butter and vanilla extract until lighter in color and fluffy. It will more than double in volume.

14. Lay the pistachio sponge cake layers out onto a large cutting board or table; trim the edges square and brush free of any crumbs. Spread a thin layer of the whipped ganâche about 1/16-inch thick on the pistachio sponge; as it rolls up, the chocolate ganâche will appear thicker. Tightly wrap up the cake rolls in a layer of parchment paper, followed by a layer of plastic wrap and put into the refrigerator to chill, 30 minutes to 1 hour.

15. Meanwhile, in a saucepan or pot that will accomodate the container of chilled ganâche, heat 1 inch of water until simmering. Heat the container of ganâche until it is melted, but not hot, stirring occasionally. It should be thick and very shiny.

16. Remove the cake rolls from the refrigerator and slice into 4-inch cylinders; remove the parchment paper or cling film before dipping into the ganâche glaze. Cool the dipped Swiss rolls in the refrigerator for 30 minutes on a piece of parchment or waxed paper before slicing on the bias; they are best served at room temperature, but easier to cut when chilled.