1. Preheat the oven to 180°C, gas mark 4. Line a 20x30cm Swiss roll tin with non-stick baking parchment, cutting into the corners to get a neat fit. Using a sieve, sprinkle this with icing sugar so that there is a fine layer more or less all over the base.
2. Beat the eggs, sugar, freeze dried strawberries and a pinch of salt with an electric whisk until you have a pale and light mixture that has quadrupled in volume. When you reach this stage, the beaters will leave a ribbon when you hold them up from the mixture.
3. Sieve over the flour and baking powder. Carefully fold together with a rubber spatula until all the flour has disappeared into the egg mixture, to form a light batter. Pour gently into the prepared Swiss roll tin. Tilt the tin to ensure the whole base is covered.
4. Bake in the middle of the oven for 15 minutes. Once cooked, it is important to act quickly. Lay a clean tea towel flat on an empty kitchen surface and cover it with a slightly smaller rectangle of baking parchment of the same shape. Take the tray out of the oven and carefully lift the sponge out of the tin, holding it by the edges of the baking parchment.
5. Place the sponge, exposed side down, on the baking parchment in the middle of the tea towel and carefully peel off the paper from the back of the cooked sponge; it will come off easily in your hands.
6. The next stage is the most important of all. Start from one end of the cloth and roll with the tea towel and parchment paper. When you come to the sponge, continue to roll it snugly, so that the sponge and towel are meshed together in a log shape. Let it stand for 10 minutes to cool and semi-set in a snail shape while you make the filling.
7. Beat the icing sugar, cream and vanilla extract for 1 minute on full blast until stiff. Put it in the fridge until needed. Once the sponge has had 10 minutes to cool off and slightly set, unroll it from its paper and tea towel, and spread a generous layer of strawberry jam all over the inside. Remove the cream from the fridge and spread it over the top of the strawberry jam. Sprinkle over the fresh strawberries.
8. Roll the bulging sponge up again and don’t worry about the mess. It’s bound to crack a little here and overspill a little there. Scatter the caster sugar all over the top and chill until needed. Take the Swiss roll out of the fridge 10 minutes before serving for a lighter result.