Add the sugar and cornstarch to a medium-sized saucepan and whisk together until no lumps remain. Add the water and lemon juice and stir together.

Heat over medium heat until the sugar begins to melt, then add the berries. Stir to coat with the sugar mixture. Continue to cook until the berries start to soften and let out juices. Use your spatula to mash the berries a bit.

Continue to cook and then remove from heat when the juices have begun to thicken, after about 3-4 minutes. Pour the mixture into another bowl and refrigerate until cool. Mixture will thicken as it cools.

If you’d like to remove the seeds, you can strain the mixture right after you finish cooking it. You can make the filling up to 2-3 days ahead, if you’d like. It should be completely cooled before adding it to your cake roll.

Preheat oven to 350°F. Line a 17×12-inch jelly roll sheet pan with parchment paper.

Whisk the flour, cocoa, baking powder, espresso powder and salt together in a medium bowl and set aside.

In a large bowl, combine the egg yolks and sugar and whisk together until well combined.

Add the sour cream, melted butter and vanilla extract and whisk together until well combined.

Add the dry ingredients and gently whisk together until well combined, then set aside.

Add the egg whites to a large mixer bowl and whip on high speed until stiff peaks form.

Gently fold about ⅓ of the whipped egg whites into the chocolate mixture to loosen up the batter.

Add the remaining egg whites and gently fold together until well combined.

Spread the cake batter evenly into the prepared pan and bake for 10-12 minutes, or until the top of the cake springs back when touched.

Remove the cake from the oven and immediately lift the cake out of the pan using the parchment paper.

While the cake is hot, roll the cake using the parchment paper. Unroll and re-roll a few times during cooling.

Let the cake cool completely for about an hour to an hour and a half.

When the cake has cooled and is ready to be filled, make the whipped cream filling. Add the heavy whipping cream, powdered sugar, cocoa powder and vanilla extract to a large mixer bowl and whip on medium speed until it just reaches stiff peaks.

Unroll the cake roll carefully, releasing it from the parchment paper.

Spread the raspberry filling evenly onto the unrolled cake.

Pipe the whipped cream on top of the raspberry filling and gently spread, as needed.

Roll the cake roll back up without the parchment paper. Use a spatula to remove any excess filling.

Wrap the cake roll up in plastic wrap with the seam side down and refrigerate for at least an hour.

To make the chocolate ganache, add the chocolate to a medium sized bowl and set aside. Heat the cream in the microwave just until it begins to boil, then pour it over the chocolate.

Allow the chocolate and cream to sit for a few minutes, then stir until smooth.

Chill the chocolate ganache until cold and firm.

Spread the chocolate ganache onto the chilled cake roll. Decorate with additional whipped cream and raspberries, if desired.

Slice the cake roll and serve.