Preheat the oven to 170ºC/gas mark 3½. Butter very well the base and sides of a 23cm diameter, 7.5cm deep, round springform tin, making sure the flat side of the springform base is uppermost (the lipped side makes it hard to remove the cheesecake).
Put the biscuits in a polythene bag, seal, then bash with a rolling pin until very fine. Tip into a bowl and mix in the butter and mint. Lightly press into the tin with a spoon. Bake for 15 minutes, then leave to cool.
For the strawberry filling, simply mix everything together in a bowl and leave for 1–2 hours for the strawberries to absorb the flavours. Drain the strawberries, reserving all the delicious juices.
For the cream cheese filling, place 3 tbsp cold water into a small, wide-bottomed heatproof bowl and sprinkle over the gelatine. Every single crystal must be wet, or it will turn to lumps later on. Set the bowl over a pan of hot (not boiling) water until every crystal has melted. Don't let it get too hot or it won't set properly.
In a small bowl, beat the cream cheese until smooth. In another bowl, lightly whip the cream and vanilla. Using an electric mixer (or handheld whisk), whisk the egg yolks and sugar until thick, pale and doubled in volume. Carefully fold in the cream cheese, then the cream. Take the strawberry juices and mix them into the gelatin liquid, sieve out any lumps, then fold in a spoonful of the cream mixture. Once well blended, gently fold in the remaining cream.
Spread the marinated strawberries over the centre of the biscuit base, ensuring they do not reach the edges. Spoon on the cream, level the surface and place in the refrigerator overnight to set.
When you are ready to serve, dip a knife into hot water, release the spring and run the knife around the edge of the tin. Ease off the base with a warm palette knife and transfer to a serving dish. Finally, decorate with the sliced strawberries and mint sprigs.