Preheat and Prepare:
Preheat your oven to 350°F (175°C). Line a 10×15 inch jelly roll pan with parchment paper and lightly grease it.

Mix Dry Ingredients:
In a bowl, sift together the flour, cocoa powder, baking powder, and salt. Set aside.

Prepare Wet Ingredients:
In a large bowl, beat the eggs and sugar together using an electric mixer on high speed until the mixture is thick and pale, about 5 minutes. Mix in the vanilla extract.

Combine Mixtures:
Gently fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix.

Bake:
Pour the batter into the prepared pan, spreading it evenly. Bake for 10-12 minutes or until the cake springs back when lightly touched.

Roll the Cake:
While the cake is still warm, carefully roll it up in the parchment paper starting from a short edge. Let it cool completely.

Make the Filling:
In a chilled bowl, beat the heavy cream and powdered sugar until stiff peaks form. Gently fold in the fresh blueberries.

Assemble the Swiss Roll:
Unroll the cooled cake and spread the whipped cream mixture over it evenly. Roll the cake back up, peeling away the parchment paper as you go.

Decorate:
Place the roll seam side down on a serving platter. Pipe whipped cream on top and garnish with fresh blueberries.