1. Get Ready: First, preheat your oven to 350°F (175°C). Line a standard jelly roll pan (about 10x15 inches) with parchment paper. This step makes lifting the cake super easy!
2. Whip the Egg Whites: In a clean, dry bowl, beat the egg whites until soft peaks form. Gradually add 1/4 cup of the granulated sugar, continuing to beat until the peaks are stiff and glossy. Set this aside gently.
3. Mix the Egg Yolks: In a separate bowl, beat the egg yolks with the remaining 1/4 cup of sugar until the mixture is light, pale, and thick. Stir in the vanilla extract for that lovely aroma.
4. Combine Dry Ingredients: Sift together the all-purpose flour, cocoa powder, baking powder, and salt. This ensures a smooth, lump-free batter. Gently fold this dry mixture into your egg yolk mixture until just combined.
5. Fold in Whites: Carefully fold the beaten egg whites into your batter. Be gentle! You want to keep all that beautiful air in the mixture for a light sponge.
6. Bake the Sponge: Spread the batter evenly into your prepared pan. Bake for 10-12 minutes, or until the cake springs back when you lightly touch it. Don't let it overbake!
7. Roll While Warm: As soon as the cake is out of the oven, lay a clean kitchen towel flat and dust it lightly with powdered sugar. Invert the warm cake onto the towel, peel off the parchment paper, and then immediately roll the cake (along with the towel) from the short end. Let it cool completely in this rolled shape – this prevents cracks later!
8. Prepare the Cream Filling: While your cake cools, grab a chilled mixing bowl. Whip the cold heavy cream with powdered sugar and vanilla extract until stiff peaks form. This will be your fluffy, delightful filling.
9. Fill the Cake: Once the cake is completely cool, gently unroll it. Evenly spread the whipped cream filling across the entire surface of the cake.
10. Re-roll and Chill: Tightly re-roll the cake from the short end. Wrap it snugly in plastic wrap and pop it into the refrigerator for at least 1 hour. This chill time helps the cake set beautifully.
11. Make the Chocolate Buttercream: In a bowl, beat the softened unsalted butter until it's light and creamy. Gradually add the powdered sugar, cocoa powder, milk (or cream), and vanilla extract. Beat until the buttercream is wonderfully smooth and fluffy.
12. Frost and Texture: Unwrap your chilled cake roll and place it on your serving platter. Spread the chocolate buttercream all over the cake, covering it completely. To get that classic tree bark look, use a fork or a spatula to create textured lines.
13. Decorate and Serve: For a final festive touch, lightly dust the entire cake with powdered sugar to mimic fresh snow. Arrange fresh, bright cranberries and sprigs of fragrant rosemary around it. Slice into delicious portions and enjoy your homemade Yule Log!