Put the rusks in a freezer bag and grind finely with a kitchen roll. Wrap the springform pan (24 cm Ø) several times in aluminium foil. Grease the mould carefully. Sprinkle with rusk crumbs.
Mix starch, sugar, vanillin sugar and lemon peel. Add quark and mix well with the whisks of the hand mixer. Add cream and eggs and stir in carefully. Fill a fat pan about 1 cm high with boiling water.
Place in the preheated oven (electric cooker: 200 °C/ gas: level 3) on the middle shelf. Pour the quark mixture into the springform pan and smooth it down. Place the pan in the fat pan and bake for 10 minutes.
Then turn down the oven (electric oven: 125 °C/ gas: level 1) and bake for another 55-60 minutes. Remove from oven and let cool on a rack. Remove from the edge of the springform pan with a sharp knife.
Remove the cake from the mould and serve on a cake platter decorated with strawberries and lemon balm as desired.