Roast the sunflower seeds in a pan without fat until golden brown, remove and let them cool down. Coarsely chop the sunflower seeds, except for 1 tablespoon. Melt butter. Put the shortbread in a freezer bag and crush it finely with a cake roll. Mix the sunflower seeds, breadcrumbs and butter well, place on the bottom of a springform pan (24 cm Ø) and press until smooth. Chill for about 30 minutes.
Soak gelatine in cold water. Wash 250 g strawberries, clean, drain and cut into small cubes. Stir cream cheese, quark, vanilla sauce powder, 125 g sugar and champagne until smooth. Whip cream until stiff. Squeeze the gelatine, dissolve and stir in 3-4 tablespoons of quark cream. Then stir into the remaining quark cream. Fold in strawberry pieces and cream one after the other. Fill the cream onto the cake base and smooth it down. Chill the cake for at least 5 hours. Wash, clean and halve the remaining strawberries. Spread the strawberries on the cake. Mix the cake glaze and 2 tablespoons of sugar in a saucepan.
Fill the cream onto the cake base and smooth it down. Chill the cake for at least 5 hours. Wash, clean and halve the remaining strawberries. Spread the strawberries on the cake. Mix the cake glaze and 2 tablespoons of sugar in a saucepan. Add 1/4 litre water while stirring, bring to the boil and remove from the heat. Spread the glaze over the strawberries from the middle. Sprinkle the rest of the sunflower seeds on top and decorate with mint