Place the puff pastry slices next to each other and let them thaw for about 15 minutes. Halve 6 slices of pastry (rectangles 5 x 10 cm). Cut 4 slices into 1 cm wide strips. Whisk the egg yolks.
Brush the rectangles with it, stick the strips of dough as a border on it and also brush with egg yolk. Place the puff pastry rectangles on a baking tray lined with baking paper. Bake in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for 15-20 minutes until golden brown.
Let the particles cool down on a cake rack. Meanwhile, separate the eggs. Cream egg yolk, fat, 50 g icing sugar, quark, lemon juice and zest with the whisk of the hand mixer. Beat the egg white until stiff, while pouring in 25 g icing sugar.
Fold the beaten egg white into the cream. Halve the melon and remove the seeds with a spoon. Quarter the melon halves. Cut the flesh from the skin and cut into thin slices. Sort the berries and wash if necessary.
Fill the puff pastry with cream and cover with the fruit. Dust with 10 g icing sugar and decorate with mint.