How can I prevent the sponge cake from cracking when I roll it into a log?
Immediately after it comes out of the oven, invert the hot sponge onto a powdered-sugar–dusted towel, peel off the parchment, and roll it up (cake and towel together) while it’s still warm; the heat sets the curve so the cake “remembers” the shape as it cools. Don’t overbake—remove the sponge as soon as it springs back to a light touch—and, before filling, brush it lightly with coffee-or-rum syrup to keep it supple.
Q2: How far in advance can I assemble the Yule Log, and what’s the best way to store it so the sponge stays soft and the ganache remains glossy?
You can fully assemble the log (filling, roll, and ganache) up to 24 hours ahead. Place it on a flat platter, tent it very lightly with plastic wrap or an inverted cake dome so the wrap doesn’t touch the ganache, and refrigerate; the cool, humid environment keeps the sponge moist while the minimal contact preserves the ganache’s sheen. About 30 minutes before serving, unwrap and let it stand at room temperature so the chocolate softens and the flavors bloom.
Can I freeze the assembled Yule Log without compromising its texture and flavor?
Yes—once the ganache has firmed, you can freeze the fully assembled log for up to one month: chill it until set, then wrap it snugly in two layers of plastic wrap followed by foil to guard against frost and odor absorption. Thaw overnight in the refrigerator (still wrapped), unwrap, and let it stand 30 minutes at room temperature; the sponge will stay moist and the filling stable, though you may want to add a fresh dusting of powdered sugar or new garnishes after thawing to restore the just-made look.