Finely crush the biscuits in the food processor. Melt the butter in a pan. Chop the white chocolate finely and melt in the butter. Mix through the cookie base.
Line a springform pan with baking paper and spread the biscuit mixture over the base. Press firmly with the back of a spoon. Place in the refrigerator until use.
For the filling, soak the gelatine sheets in a bowl of water.
Mix the cream cheese and goat's cheese with a hand or stand mixer until loose and fluffy. Add the sugar, vanilla sugar and whipped cream. Beat together until thick and firm.
Squeeze the gelatine and melt briefly in a saucepan, then add to the goat's cheese mixture while whisking.
Spoon the goat's cheese mixture into the springform pan and smooth out. Leave to set in the fridge for at least 2 hours.
Meanwhile, slice the pears. Put them in a pan with the elderflower syrup and the water and boil them for 15 minutes. Let it cool completely.
The best way to get the cheesecake out of the mould is to heat it from the outside, for example with a hairdryer or a hot wet tea towel. Carefully remove the ring of the springform and before serving, place the pears on the cake.