Preheat your oven to 350F and line a baking tray with parchment paper (30x40cm). Place aside.
Mix the eggs with sugar in the bowl of your mixer and whip for 8-10 minutes until tripled in volume.
Sift the flour with cocoa powder and salt then fold the flour into the whipped eggs. Add one spoon at a time and fold with a spatula.
Take a few tablespoons of batter in a small bowl and stir in the butter.
Transfer the mixture back to the bowl and fold it in slowly and gently.
Pour the batter into your prepared pan and bake in the oven for 10-15 minutes or just until the top is set and springs back is pressed slightly. Don't bake more than 15 minutes as it will dry out.
Remove from the oven and let it cool completely.
Melt the chocolate and 50ml heavy cream in a heatproof bowl over a hot water bath.
Remove from heat and let it cool to room temperature.
Stir in the vanilla then fold in the whipped cream. Place the mousse in the freezer for 30 minutes.
Spread the mousse over the chocolate sponge and top with diced strawberries.
Roll the sponge tightly and place on a platter. Place in the fridge until the ganache is ready.
Bring the cream to the boiling point in a saucepan and remove from heat.
Stir in the chocolate and mix until melted.
Add the vanilla and let it cool completely. At this point, you have two options: either you pour the ganache over the roll or you place the ganache in the fridge and let it set then spread it with a spatula. I chose the second option as I wanted to create the look you see, but it's up to you.
Decorate the roll with chocolate shavings and fresh strawberries and serve it chilled.
Recipe by Pastry Workshop at http://pastry-workshop.com/chocolate-mousse-cake-roll-rulada-cu-mousse-de-ciocolata/