Step 1: Prepare the Baking Pan

1. Preheat oven to 350°F (175°C).
2. Grease and line a 15×10-inch jelly roll pan with parchment paper.

Step 2: Mix the Dry Ingredients

1. In a medium bowl, sift together flour, cocoa powder, baking powder, and salt.
2. Set aside.

Step 3: Prepare the Egg Mixture

1. In a large mixing bowl, beat the eggs and granulated sugar until light and fluffy (about 4-5 minutes).
2. Stir in the milk and vanilla extract until combined.

Step 4: Combine the Batter

1. Gently fold the dry ingredients into the egg mixture, ensuring the batter stays light and airy.

Step 5: Bake the Cake

1. Pour the batter into the prepared pan and spread evenly.
2. Bake for 10-12 minutes, or until the cake springs back when lightly touched.

Step 6: Roll the Cake While Warm

1. While the cake is baking, dust a clean kitchen towel with powdered sugar.
2. Once baked, immediately invert the cake onto the towel and gently peel off the parchment paper.
3. Roll the cake tightly with the towel and let it cool completely.

Step 7: Make the Filling

1. In a bowl, whip heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form.

Step 8: Assemble the Swiss Roll

1. Unroll the cooled cake and spread the whipped cream filling evenly.
2. Roll the cake back up without the towel.
3. Transfer to a serving platter.

Step 9: Decorate & Serve

1. Dust with cocoa powder or chocolate shavings.
2. Slice and serve chilled or at room temperature.