• Drain the pineapple can and save the syrup. Pour the syrup into a wider bowl. Or you could drain the mandarins first and use their syrup instead, whichever you prefer.
• Dip each ladyfinger in the syrup, very shortly, they should barely get wet and not get soaked.
• Arrange the ladyfingers, standing and with the sugared side facing the outside of the form, inside the ring of a 24-26 cm/ 9.5-10.2 inch springform.
• After lining the springform with the biscuits, arrange some of them on the bottom of the springform as well. Break 1 or 2 ladyfingers and fit the pieces in the gaps, the whole base of the pan should be covered with ladyfingers.
• Chop the pineapple rings (or use already chopped pineapple). Drain the mandarins as well very thoroughly.

Custard:

• Place the 5 egg yolks into a small pan. Add the sugar, corn starch, and vanilla essence. Whisk well until smooth. Slowly start adding the milk while whisking all the time.
• Turn on the heat and heat the mixture while whisking continuously until it comes to a boil, it will take about 10 minutes. Let bubble once or twice until slightly thickened. Set the custard aside for 10 minutes.
• In the meantime soak the gelatin granules according to the packet's instructions. In my case (Dr. Oetker gelatin granules) I soaked them in 10 tablespoons cold water for 10 minutes.
• Add the bloomed gelatine to the warm custard and whisk well to incorporate. Transfer the mixture to a large bowl. Place a piece of cling film on top (it will prevent the custard from getting a “skin”) and let it come to room temperature. It will take about an hour, don't let it stand longer than necessary or the custard will set and the finished Charlotte will get clumpy after adding the whipped cream. It has to be completely cooled, but not completely set.
• When the custard has reached room temperature, beat the heavy cream until stiff. Set 3-4 tablespoons of the whipped cream aside for the decoration of the cake. Fold the rest of the whipped cream gradually and carefully into the custard.
• Set some of the pineapple pieces, mandarins, and grapes aside for the decoration of the cake. Fold the rest of the fruit into the custard-cream mixture.
• Pour the filling into the prepared pan and arrange the remaining fruit on top.
• Pipe the remaining whipped cream on top of the cake as well.
• Place the cake in the fridge and let it get set overnight.