Preheat the oven to 220C/200C fan/gas 7. Grease and line a 24x20cm/9.5x8in lipped baking tray.
For the sponge: cream the eggs and sugar together in a large bowl for 4-5 minutes until pale and fluffy.
Sift the flour and cocoa powder into the egg and sugar mixture and fold until combined, then stir in the melted butter. Pour the mixture into the prepared baking tray and bake for 18-20 minutes, or until the cake is risen and is springy to the touch.
Remove from the oven and allow to cool briefly in the tray before turning out onto a wire rack to cool completely.
For the ice cream: place the chocolate and butter in a heatproof bowl set over a pan of just-simmering water (make sure the water doesn’t touch the bottom of the bowl). Stir continuously, until the chocolate has melted and the mixture is smooth and glossy. Set aside.
Place the sugar and water into a small saucepan set over a low heat, stirring until the sugar has dissolved. Increase the heat and bring to the boil, cooking for a few minutes until the mixture thickens to a syrup consistency. Set aside to cool for one minute.
Place the egg yolks in a heatproof bowl set over a pan of just-simmering water (make sure the water doesn’t touch the bottom of the bowl). While whisking continuously, slowly trickle in the hot sugar syrup. When all of the sugar syrup has been incorporated and the mixture has thickened, whisk in the double cream and the melted chocolate mixture until smooth.
Pour the mixture into the bowl of an ice cream machine and churn according to the manufacturer’s instructions. Scoop the churned ice cream into a rectangular container, smoothing the top, and place into the freezer. Remove from the freezer 5-10 minutes before serving.
For the meringue: place the water, sugar and glucose (if using) into a heavy-based saucepan. Place over a medium heat, stirring frequently, until the mixture comes to the boil. Increase the heat to high and boil until the mixture reaches 121C (check using a sugar thermometer), then quickly remove from the heat.
. Beat the egg whites and vanilla seeds in a stand mixer, then carefully pour the sugar syrup onto the beaten egg whites in a thin stream, taking care not to let the syrup run onto the whisks or the edge of the bowl. Continue to beat at a low speed until the mixture is almost completely cold – this will take about 10 minutes. Spoon the meringue into a piping bag and set aside.
. For the cherry sauce: place all of the cherry sauce ingredients into a pan and cook over a medium heat until the cherries are tender (add a splash of water if the mixture looks too dry). Transfer the mixture to a food processor and blend to a smooth puree. Pass the sauce through a fine sieve.
. To assemble the baked Alaska, cut two equal-sized rectangles from the sponge. Cut the ice cream into a brick shape the same length and width as the sponge.
. Place one sponge rectangle onto a serving plate and drizzle with kirsch, then smooth over some of the cherry sauce. Top with the ice cream, then the other sponge to make a ‘sandwich’. Pipe the meringue all over the ‘sandwich’ to cover, making sure it is completely covered.
. Using a mini blowtorch, brown the meringue all over. Place the whole cherries around the base of the meringue to decorate. Pour some kirsch into the egg shell and press into the top of the meringue. Carefully ignite the kirsch just before serving.