Put the rusks in a freezer bag and crumble them finely with a rolling pin. Melt butter in a pot and mix well with rusk, 125 g sugar and about 4 tablespoons of cold water. Grease a springform pan (26 cm Ø) and press the crumbs onto the bottom and the edge (2-3 cm high). Put the tin in a cool place for about 20 minutes. In the meantime, drain mandarins well on a sieve.
Whisk eggs, remaining sugar and vanilla sugar with the whisk of the hand mixer until thick and frothy (4-5 minutes). Mix curd, cream cheese, flour, orange and lime peel and orange juice until smooth and stir into the egg foam. Spread the mandarins, except for a few for decoration, on the rusk. Add the cream cheese mixture and smooth it down. Bake in the preheated oven, 2nd shelf from below (electric oven: 150 °C/ gas: level 1) for approx. 35 minutes. Then switch the oven up (electric oven: 175 °C/ gas: level 2) and bake in approx. 45 minutes. Carefully remove the cake from the edge with a sharp knife and let it cool down in the tin on a cake rack. Remove the cake from the tin and decorate with mandarin slices, lime slices and lemon balm leaves. Serve with semi-stiff whipped cream.
Bake in the preheated oven, 2nd shelf from below (electric oven: 150 °C/ gas: level 1) for approx. 35 minutes. Then switch the oven up (electric oven: 175 °C/ gas: level 2) and bake in approx. 45 minutes. Carefully remove the cake from the edge with a sharp knife and let it cool down in the tin on a cake rack. Remove the cake from the tin and decorate with mandarin slices, lime slices and lemon balm leaves. Serve with semi-stiff whipped cream. Makes 12-16 pieces