Step 1

Preheat your oven to 180°C (350°F)Prepare your pan. Grease with butter or spray with non-stick spray the base and sides of a 25x38cm (10x15-inch) baking pan /swiss roll pan/jelly roll pan. Line the pan with parchment paper, ensuring the paper overhangs the pan's sides. This will help you later when trying to remove the sponge from the tin. Grease the parchment paper with butter, as this will help with peeling the paper off once the sponge has baked.

Step 2

Whisk egg whites. Using handheld electric beaters or in the bowl of a stand mixer fitted with the whisk attachment, whisk the egg whites on medium to high speed until soft peaks form.

Step 3

Whip the egg yolks and sugar. In a separate bowl, whip the egg yolks, sugar and vanilla extract on medium-high for 5 minutes until the mixture is light and creamy. When lifting out the whisk, you want to see trails of the mixture on the surface of the batter for a few seconds.

Step 4

Sift dry ingredients. Into a separate bowl, sift in the flour, cocoa powder, baking powder and salt and whisk together.Add dry ingredients and add egg whites in two parts. Add half the cocoa flour mixture directly to the egg yolk mixture in the bowl. Add in half the egg whites. Using a rubber spatula, fold the mixture until the flour and egg whites are just incorporated. Then, add the remaining cocoa flour mixture and the remaining egg whites. Again, fold through until just a few flour streaks remain. This will ensure that you don't overmix. Fold them in with a light touch to maintain all the trapped air. This is one of the reasons why the sponge is so light and airy.

Step 5

Pour the batter into the prepared pan and shake/wiggle the pan to help guide the batter into the pan's corners. Use an offset spatula if necessary to help smooth out the batter.Bake in the oven for 10-12 minutes until a toothpick inserted into the centre comes out clean and springs back when pressed lightly.Cool: Remove the baking pan from the oven and set it on a wire rack to cool for ten minutes until the sponge is warm and not steaming hot. It's important not to miss out on this step.

Step 6

Prepare your tea towel. Whilst the sponge is baking, lay a tea towel or piece of parchment paper on your work surface and dust generously with cocoa powder. (Alternatively, sprinkle with caster sugar or dust with powdered icing sugar).

Step 7

Invert the sponge onto the tea towel. Once the sponge has baked, remove it from the oven and immediately invert the sponge onto the tea towel whilst it is still hot. Peel off the parchment paper. Gently peel off the parchment paper on the bottom of the sponge. Roll sponge up. Starting from the sponge's short end, using your hands, roll the sponge up gently but firmly until it is totally rolled into the tea towel (or parchment paper). Set the roll aside with its seam side down to cool completely.

Step 8

Whilst the sponge roll is cooling, make the cream cheese frosting. If you are using Cream Cheese from a tub, place the cream cheese into the centre of two pieces of paper towel. Fold the paper towel around the cream cheese and pat it firmly to remove some of the moisture. Repeat this on another two pieces of paper towel. Set to one side. (There is no need to do this step if using Philadelphia in brick/block form).

Step 9

Whip the butter and vanilla extract. In the bowl of a stand mixer fitted with the paddle attachment, add the butter and vanilla extract and beat on high for 4 minutes until pale and creamy. Add in the powdered icing sugar and beat until mixed in. Continue to beat for another two minutes. Add in the cream cheese and beat on medium speed until mixed through. The frosting should be smooth but firm enough to hold its shape. Refrigerate for 20-30 minutes.

Step 10

Unroll, fill and re-roll. Gently unroll the sponge once it has cooled. Spread the cream cheese filling evenly over the sponge's surface, leaving a 2cm (1-inch) gap around the edge. Re-roll the sponge up again and wrap it in parchment paper and then in plastic wrap for the roll to hold its shape. Refrigerate for 1-2 hours for the filling to firm up.

Step 11

Before serving, make the chocolate ganache. Place the chopped chocolate and butter into a medium bowl. In a small saucepan, heat the cream gently on low heat until simmering around the edges. Pour the cream over the chocolate into the bowl and sit for a couple of minutes. Then whisk continuously until the chocolate is smooth and the butter has melted.

Step 12

Cover swiss roll. Place the swiss roll onto a wire rack set on a baking tray. Slowly pour the ganache to coat the roll. Use an offset spatular to smooth the chocolate all over. Decorate with blackberries if desired and let the chocolate set for 20 minutes before slicing ends to neaten up the roll before serving. See tips below for slicing.