Instructions

1. Preheat the oven to 350 degrees F. Spritz a 12”x17” sheet pan with nonstick cooking spray, making sure to get the sides, and line with a sheet of parchment paper. Do one more spritz of cooking spray to coat the parchment. If using oil instead, dab a teaspoon of vegetable oil on a paper towel and coat the parchment, making sure to add just enough to leave a slick sheen on the paper. Be sure all of the exposed pan and parchment have been lightly greased with oil or spray.

2. In a stand mixer with a paddle attachment or a mixing bowl with an electric beater, beat the eggs with the granulated sugar on high until thick and very pale and doubled in size, about 4 to 5 minutes. Mix in vanilla extract. In a small bowl, whisk together the flour, baking powder, and salt. Gently fold this mixture into the egg mixture with a rubber spatula until just combined.
3. Spread the batter into a thin, even layer on the prepared pan. Bake for 12 to 15 minutes, until the surface of the cake springs back lightly when touched. You also want to see the lumps on the cake surface turn ever so slightly tan. Do not let the cake brown more than that; if the cake overbakes, it will be too stiff to roll out. Note that a light-colored silver pan might take slightly longer to bake, whereas a darker pan should be checked right at 12 minutes.
4. While the cake is baking, set out a clean kitchen towel that is at least as large as the sheet pan, and place another piece of parchment paper directly on top of the towel. On top of the new piece of parchment, using a mesh strainer or sieve, sift 1 tablespoon of powdered sugar all over to coat. This is to prevent potential sticking when you unroll the cake later.
5. Remove the cake from the oven. Using a thin knife or offset spatula, loosen the cake from the edges of the pan. Be careful to not drag the knife along the edges too quickly; this could tear the cake. While the cake is still hot, using oven mitts, carefully but swiftly invert the pan upside down onto the new piece of parchment paper on the kitchen towel. Very gently and slowly peel off the parchment paper stuck to the bottom of the cake; peeling it too quickly could tear the cake. Sift another tablespoon of powdered sugar evenly over the exposed cake, also to prevent further sticking.
6. Starting from the short end of the cake, roll the cake gently with the towel, lifting the edge of the towel to guide you. Roll it all the way so the cake is completely rolled in a cylinder shape. Let it cool completely at room temperature while rolled up.
7. Meanwhile, prepare the espresso and rum. Combine cooled espresso and rum in a small bowl and set aside.
8. To prepare the mascarpone buttercream, in a mixing bowl, beat together the softened mascarpone and butter until smooth and creamy and no lumps remain. Gradually add powdered sugar, salt and vanilla extract, beating on high speed until well combined and very fluffy. If the frosting ever appears curdled or broken, it is because the butter or mascarpone are too cold; simply allow the mixture to become room temperature and continue to mix. If it seems at all gluey or too thick, continue to beat the mixture until it gets fluffy and spreadable. Set aside.
9. To assemble the yule log, carefully unroll the cooled cake. Brush the surface of the cake evenly with the espresso rum mixture. If any parts of the cake are noticeably thicker, add more to those spots; and if any parts of the cake appear thin, use very sparingly on those parts. Once the syrup has soaked into the cake, spread a layer of the mascarpone buttercream evenly over the cake, leaving a small ½” border around the edges.
10. Gently roll the cake back up, using the towel to help lift and guide it. Gently peel the parchment paper off as you roll. Place the seam side of the cake down on a serving platter or tray. Set the cake into the refrigerator to set for about 30 minutes.
11. After the 30 minutes, you have the option to cut a diagonal edge off the short side of the cake that you can then place to the side of the cake to simulate the stump of a branch, as pictured above. However, this is an optional step.
12. Meanwhile, make the chocolate ganache. Place the chopped chocolate in a heatproof bowl. Heat the heavy cream in a saucepan until it just starts to simmer on the edges. Pour the hot cream over the chocolate. Let it sit for a minute, then stir until smooth and glossy. Allow the ganache to cool for about 5 minutes to thicken slightly before spreading over the cake. (If any lumps remain, simply microwave the mixture in 15 second increments until it is smooth.)
13. Carefully pour the chocolate ganache over the prepared yule log, using a spatula to spread it evenly over the cake. Wipe off any excess ganache off the plate with a paper towel, if needed. While the ganache is still slightly soft, press toasted sliced almonds onto the surface in a shingled manner to create the "bark" effect. You can also press them directly onto the cake without the shingled affect. Chill the log in the refrigerator for at least an hour to set the ganache, but optimally overnight to allow the tiramisu flavors to marry.
14. To serve, dust with cocoa powder and powdered sugar if desired. Slice and serve!