For the sponge: Preheat the oven to fan 170C/150C fan/gas mark 4. Lightly oil two 18cm cake tins. Line the base with baking parchment and lightly oil. Dust the sides of each tin with caster sugar and then with flour.
2. Sift the flour and a pinch of salt together and set aside. Place the eggs and sugar in a large bowl. If you have an electric whisk, beat until the mixture is pale and thick and leaves a trail when you lift the whisk. If you’re whisking by hand, place the bowl over a pan of just-boiled water (off the heat); whisk until it is pale and thick, then remove from the pan and continue to whisk until cool.
3. Tip the flour over the surface of the whisked egg mixture and, using a flat metal spoon, gently fold the flour into the mixture. Divide between the two tins and bake for 20 minutes or until golden. Test by lightly pressing the cake with your fingertip: it will spring back if cooked. Leave the cakes in their tins on a wire rack for 5 minutes. Turn out the cakes and peel off the baking paper. Dust the top of one cake (baked-side up) with caster sugar. Leave until cold.
4. For the strawberry filling: Meanwhile, toss the strawberries with the kirsch and sugar. Once the cakes are cold, whip the cream until it forms soft peaks. Fold in the strawberry mixture. Spread over the bottom sponge, leaving a clear edge for the cream to squeeze into when you add the top. Gently squash on the sugared top and add a further dusting of caster sugar.
5. If using, top with a freshly cut rose for serving but remember to remove before cutting in to the cake.