1. Prepare the Pan and Oven:

• Preheat oven to 375°F (190°C).
• Grease the jelly roll pan. Line it with parchment paper, leaving a slight overhang on the short sides for easy lifting. Grease the parchment paper as well. Dust lightly with flour or cocoa powder, tapping out the excess.

2. Make the Sponge Cake Batter:

• In a large bowl, beat the egg yolks with ½ cup (100g) of the granulated sugar using an electric mixer on high speed until pale yellow, thick, and ribbony (about 3-5 minutes). Beat in the vanilla extract and melted butter/oil.
• In a separate, clean, dry bowl, beat the egg whites with an electric mixer on medium speed until soft peaks form. Gradually add the remaining ¼ cup (50g) of granulated sugar, beating on high speed until stiff, glossy peaks form. Be careful not to overbeat.
• Sift the flour, cocoa powder, baking powder, and salt together into a small bowl.
• Gently fold about one-third of the beaten egg whites into the egg yolk mixture to lighten it.
• Alternately fold in the remaining egg whites and the sifted dry ingredients in two or three additions, starting and ending with the egg whites. Fold just until combined – be careful not to deflate the batter.
• Spread the batter evenly into the prepared jelly roll pan, making sure it reaches the corners.

3. Bake the Sponge:

• Bake for 12-15 minutes, or until the cake springs back when lightly touched in the center. Do not overbake, as this will make it prone to cracking when rolled.

4. Roll the Cake:

• While the cake is baking, lay a clean kitchen towel flat on your work surface and dust it generously and evenly with powdered sugar or cocoa powder.
• As soon as the cake comes out of the oven, immediately invert it onto the prepared towel.
• Carefully peel off the parchment paper.
• While the cake is still hot, starting from one of the short ends, gently but firmly roll the cake up with the towel inside.
• Place the rolled cake (seam-side down) on a wire rack and let it cool completely in the towel (at least 1 hour).

5. Prepare Syrup and Filling (While Cake Cools):

• Syrup (Optional): In a small saucepan, combine water/cherry juice and sugar. Bring to a simmer, stirring until sugar dissolves. Remove from heat and stir in the Kirsch. Let cool completely.
• Filling: Pat the drained cherries very dry with paper towels. You can chop them slightly if desired. In a large, chilled bowl, whip the cold heavy cream with the powdered sugar and vanilla extract using an electric mixer until stiff peaks form. If using, fold in the Kirsch.

6. Assemble the Roulade:

• Carefully unroll the cooled cake, removing the towel.
• If using syrup, gently brush it evenly over the inside surface of the cake.
• Spread about two-thirds of the whipped cream filling evenly over the cake, leaving about a 1-inch border along the far short edge.
• Scatter the drained, dried cherries evenly over the cream.
• Carefully re-roll the cake (without the towel this time), starting from the same short end you started rolling from initially. Try to roll it tightly but gently.
• Place the roll seam-side down on a serving platter or cutting board.

7. Chill and Garnish:

• Chill the cake roll in the refrigerator for at least 2 hours (or up to overnight) to allow the filling to set and make slicing easier.
• Before serving, you can trim the ends for a neater appearance (optional).
• Spread or pipe the remaining whipped cream over the top and/or sides of the roll.
• Garnish generously with chocolate shavings/curls and fresh cherries, if desired.

8. Serve:

• Slice the chilled Black Forest Roll Cake using a sharp, serrated knife, wiping the blade clean between cuts if necessary.