Step 1: Preheat your oven to 375°F (190°C). Line a 15×10-inch jelly roll pan with parchment paper, extending it over the sides for easy lifting. Grease the parchment paper lightly.
Step 2: In a medium bowl, sift together the all-purpose flour, unsweetened cocoa powder, baking powder, and salt. Set aside.
Step 3: In a large bowl, using an electric mixer, beat the room temperature eggs and granulated sugar on high speed for 5-7 minutes, or until the mixture is very thick, pale yellow, and has tripled in volume. Beat in the vanilla extract.
Step 4: Gently fold the dry ingredients into the egg mixture in two additions, being careful not to deflate the eggs. Fold until just combined; do not overmix.
Step 5: Pour the batter evenly into the prepared jelly roll pan. Spread gently to the edges with an offset spatula. Bake for 12-15 minutes, or until the cake springs back when lightly touched and a toothpick inserted into the center comes out clean.
Step 6: While the cake is baking, lay a clean kitchen towel on your counter and dust it generously with powdered sugar. Immediately upon removing the cake from the oven, invert it onto the sugared towel. Carefully peel off the parchment paper.
Step 7: Starting from a short end, carefully roll the cake (along with the towel) into a tight log. Place it seam-side down on a wire rack and let it cool completely, about 1 hour.
Step 8: For the Coconut-Pecan Filling: In a medium saucepan, combine the evaporated milk, granulated sugar, egg yolks, and butter. Cook over medium-low heat, stirring constantly, until the mixture thickens to a pudding-like consistency (about 10-12 minutes). Do not boil.
Step 9: Remove from heat and stir in the vanilla extract, shredded coconut, and chopped pecans. Let the filling cool completely to room temperature.
Step 10: For the Chocolate Ganache: In a small saucepan, heat the heavy cream until it just begins to simmer. Do not boil. Remove from heat.
Step 11: Place the chopped semi-sweet chocolate in a heatproof bowl. Pour the hot cream over the chocolate and let it sit for 5 minutes without stirring.
Step 12: After 5 minutes, gently whisk the mixture until smooth and glossy. If desired, stir in 1 tablespoon of butter for extra shine. Let the ganache cool slightly until it’s spreadable but not too runny.
Step 13: Assembly: Once the cake is completely cool, carefully unroll it. Spread the cooled coconut-pecan filling evenly over the entire surface of the cake, leaving a ½-inch border around the edges.
Step 14: Starting from the same short end you rolled it from initially, carefully and tightly re-roll the cake. Transfer the rolled cake to a serving platter, seam-side down.
Step 15: Pour the slightly cooled chocolate ganache over the top, letting it drip down the sides. Garnish with extra toasted pecans or chocolate shavings if desired.
Step 16: Refrigerate for at least 30 minutes to allow the ganache to set and the flavors to meld, making it easier to slice. Serve chilled and enjoy your german chocolate roll cake recipe delightful dessert!