This might seem like a complicated recipe, but as long as you're organised, in fact it is quite straightforward. Looks good, and tastes excellent!
The version I made which I photographed for this post used genoise sponge as a base; by preference I would use a biscuit crumb base, as in a cheesecake, not least because in this house something this size is never going to be consumed at one sitting, and so you really want a base which won't go soggy if left for more than several hours.
These ingredients make 1 x 23 cm gateau.
Biscuit crumb base, using ten digestive biscuits (approximately) and 50g butter- blitz the biscuits along with the melted butter in a food processor, and then press into the base of a lined 23 cm spring form mould, and bake for ten minutes in a 180 degree C oven.
Mousse: 6 tsp powdered gelatine; 400g blackcurrant puree; italian meringue, made using 190g sugar, 45 ml water and 100ml egg white; 150 ml whipping cream.
Glaze: 2 tsp powdered gelatine; 50g sugar; 150 ml creme de cassis; 1/4 cup fresh blackcurrants.
1. Grease a 23 cm spring form tin, and line the base with greaseproof paper. Make the biscuit base, and allow it to cool in the tin.
2. For the mousse, heat the puree and powdered gelatine together in the top of a double boiler; once you are sure the gelatine has all dissolved, take off the heat and allow it to cool.
3. Make the italian meringue: heat the sugar and water together over medium heat until they reach 122 degrees C; whisk the egg white until it begins to be dense, and then pour the sugar syrup into it, whilst whisking, and continue to whisk until it is properly stiff, and has significantly cooled (perhaps five minutes of whisking); fold into this the cooled blackcurrant puree, and then fold into this the cream, which has been beaten until it holds its shape. Pile this mixture into the tin, on top of the biscuit base. Smooth the top, and refrigerate for at least four hours, to allow the mousse to set.
4. To make the glaze, add the sugar to the cassis and the blackcurrants in a small pan and heat gently, until the sugar has entirely dissolved; . Off the heat, stir in the gelatine, and gently pour the glaze over the top of the mousse, making sure that the blackcurrants are more-or-less evenly spaced. Return the tin to the fridge for a further hour or so, until the glaze has also set.
To un-mould, run a warm knife around the inside of the tin, to free the mousse before releasing the tin.