Start by preheating your oven and lining your baking sheet with parchment. Mix your dry ingredients, then beat the eggs and sugar until fluffy. Fold in the dry ingredients gently to keep the sponge light and airy.
Pour the batter into the prepared pan and bake for 12-15 minutes. While it’s hot, lift the cake with parchment and roll it tightly from the short side. Let it cool completely to hold its shape.
Whip mascarpone cheese, heavy cream, powdered sugar, and vanilla until smooth and light. Unroll the cooled cake and spread the filling evenly, leaving a small edge to prevent spillage.
Gently roll the cake back up, wrap in plastic, and refrigerate until firm. This keeps the cake intact and makes it easier to decorate.
Melt chocolate with butter and let it cool slightly. Whip to a lighter texture if desired, then spread over the cake. Cut a small piece of the log to attach as a branch and create a realistic Yule Log effect.
Use a fork to add bark-like lines on the ganache, then garnish with sugared cranberries and rosemary sprigs for a festive presentation.