The tricky part of this impressive dessert is making the domes – but care and patience will reward you with big compliments from your guests.
Preheat the oven to 180°C/160°C fan/350°F/Gas 4.
Make the brownies. Place the sugar and softened butter in a bowl and mix together with an electric hand whisk until light and creamy. Gradually beat in the eggs, then beat in the cocoa and flour. Stir in the chocolate chips and Chambord. Spread the mixture in the prepared tin and bake for about 25–30 minutes, until the top is firm but springy. Leave the brownies to cool in the tin a little, then turn out onto a wire rack to cool completely.
Meanwhile, make the chocolate balls. Put 450g of the chocolate in a bowl suspended over a pan of gently simmering water, until it reaches 42°C/108°F on a sugar or chocolate thermometer. Remove the bowl from the pan, add the rest of the chocolate and stir until melted and the heat has reduced to 28°C/82°F. Put the bowl back on the pan of simmering water, and reheat the chocolate to 31°C/88°F. Remove the bowl from the heat.
Blow up the balloons to about 12.5cm in diameter. Place 1 balloon onto each of the 4 glass tumblers, tied end downwards. One by one, hold the tied end and dip the balloons into the melted chocolate to cover at least half way up the sides, resting them back on the glasses as you go. Transfer to the fridge for at least 15 minutes, to set.
Once set, carefully dip each balloon again, this time chilling for 30 minutes, until set hard. Snip the tied end of the balloon to deflate, then very carefully peel the balloon away from the chocolate. Place the domes on the lined baking tray and keep chilled.
Use the blowtorch to heat a metal tray or nonstick frying pan, then carefully melt the bottom of each dome to make an opening large enough to go over the dessert. Chill the domes again for 5 minutes, then heat a 3cm round cutter on the hot surface of the metal tray or frying pan and press onto the chocolate domes to cut holes. Chill the domes again until you’re ready to serve.
Make the mascarpone cream. Whisk together all the ingredients until thick and combined, then place in a small, disposable piping bag.
Make the syllabub. Put half the raspberries in a bowl, squash them with a metal spoon and sprinkle over the sugar. (Reserve the other half to serve.) Put the cream in a separate bowl and stir. Fold the Chambord and the sweet wine into the cream, then stir in the crushed raspberries. Set aside.
To make the coulis, place the raspberries in a frying pan with the lemon juice, Chambord and icing sugar. Place over a medium heat and cook for 2–3 minutes, until softened. Push the mixture through a sieve into a small bowl or jug. Discard the pips.
Cut out rounds of brownie using the 6.5cm cutter and slice each round in half, to make 2 discs (8 discs altogether). Drizzle the discs with Chambord.
Place 1 disc on each of 4 serving plates. Snip the end of the piping bag and pipe cream on each disc, top with the remaining discs and spoon on the syllabub. Top with a couple of the reserved fresh raspberries and place 1 chocolate dome over each prepared dessert. Spray with edible gold dust, then decorate the plate with a few more fresh raspberries. Chill each dessert until you’re ready to serve.
To serve, heat the coulis in a small pan over a medium heat until hot, then serve in a little jug or cup for your guests to spoon over the domes, so that the domes melt to fully reveal the dessert inside.