Chopping chocolate. Warm the cream in a pot. Add brandy and chocolate and melt in it while stirring. Cover and chill for at least 5 hours.
Line two baking trays with baking paper. Place the puff pastry slices one beside the other on a baking tray and let them thaw for about 10 minutes. Preheat the oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer).
Roast the almonds in a pan without fat. Remove and chop roughly. Add sugar and 4 tablespoons of water to the pan and caramelise over medium heat until golden. Stir in the almonds and pour the mixture onto the second baking tray. Quickly spread flat. Let it cool down.
Prick the puff pastry slices several times with a fork. Whisk the egg and brush the dough with it. Bake in a hot oven for about 15 minutes, dusting thinly with icing sugar halfway through the baking time. Remove and let cool off.
Whip the chocolate cream with the whisk of the mixer until creamy. Cut both slices of dough in half horizontally. Spread 2 lower slices and 1 upper slice loosely with 1⁄3 chocolate cream each. Place on top of each other and cover with the last upper slice of dough. Dust with icing sugar. Break the brittle roughly and decorate the puff pastry slices with it. Serve immediately.