Set aside 175 g of the chocolate and the walnuts. Melt the remaining chocolate with the butter in the MELTO melting pot in a water bath. 
Beat the sugar, salt and eggs until fluffy, then stir in the chocolate-butter mixture. Mix flour with the baking powder and stir into the egg mixture. Then fold in the chocolate-nut mixture. 
Grease a baking tray and spread the batter evenly in it. 
Bake at 180 °C for about 30 minutes. 
Divide the grapes into quarters using the FLEXICUT vegetable and fruit divider. Bring the grape juice to the boil with the sugar and thicken with a little cornstarch. Add the quartered grapes. 
Mix the egg whites with the sugar and beat with a mixer until whipped egg whites form. Place the beaten egg whites in a piping bag, pipe onto the plate and brown with a FUEGO flambe burner.