Melt all the chocolate together in a glass bowl over a pan with hot water, taking care not to let the bowl touch the water. Once melted set aside to cool.
Beat the eggs and sugar in a bowl until thick and pale. Using a metal spoon, fold the chocolate into the egg mixture. Gently fold in the crushed hazelnuts and brandy and then the whipped cream.
Divide the raspberries and strawberries between four dessert glasses. Place some of the chocolate mixture on top until you three-quarters fill the glass. Place slices of mango on top and finally fill the glass with the remaining chocolate mixture. Refrigerate for at least one hour until set.
Just before serving decorate with a slice of mango and a strawberry.