Soak the gelatine leaves in cold water until soft. Purée the raspberries then pass through a sieve over a bowl and discard the seeds. Set aside.
Pour the milk into a pan and heat until just under boiling point. Whisk the egg yolks and caster sugar together until pale and creamy. Pour the hot milk over the eggs and whisk together. Return the custard to the pan and cook until the mixture coats the back of a spoon. Do not boil as this will split the custard. Remove from the heat, then drain the gelatine, squeezing out any excess moisture and add it to the custard. Mix well then transfer to a clean bowl and leave to cool slightly. Fold in the raspberry purée then leave to cool for at least 30 minutes.
Line each muffin hole with cling film, to help turn them out. Using a really sharp knife slice the Swiss roll into really thin slices- no more than 6mm deep- you should get at least 20 slices. Use 12 slices to line the bottom and as much of the sides of each muffin hole as possible. Unravel the remaining Swiss roll slices and use to fill up the sides of the holes, until they are 1cm from the top of the holes. Use any offcuts to patch any holes so that the filling doesn’t seep through.
In a bowl, whip the cream until soft peaks form and stir into the raspberry bavarois then spoon into the lined holes. You should need 3-4 teaspoons of filling for each hole.
Use the remaining middles of slices of Swiss roll to top each filled muffin hole and press gently to seal, making sure none of the filling comes out. The process is fiddly but you will end up with 12 neat Swiss roll domes, sealed with a solid sponge base.
Close the cling film over the top of the royales, and chill in the fridge for a minimum of 4 hours, or overnight until set.
Gently pull the cling film to release each Charlotte and turn all 12 cakes out.
Decorate each cake with a little whipped cream and some extra raspberries.