Preheat the oven to 180°C/Gas Mark 4. Brush the base and sides of a 20cm (8in) Aluminium PushPan with a little melted butter. If using a normal cake tin, line the base and sides with baking parchment.
Add the biscuit crumbs and caster sugar to the remaining melted butter and stir well. Tip into the cake tin and press into an even layer. Bake for 10 minutes, then cool on a wire rack while preparing the filling. Increase the oven temperature to 220°C/Gas Mark 9.
To make the filling, beat the soft cheese for a few seconds in a large bowl with a handheld electric mixer on a low speed, until just creamy. Gradually beat in the caster sugar. Sprinkle in the cornflour and beat again for a few seconds until fully incorporated, then stir in the lemon paste.
Add the eggs a little at a time, beating between each addition on a low/medium speed. Stir in the double cream with a large metal spoon.
Pour the filling over the base. Bake for 10 minutes, then reduce the temperature to 110°C/Gas Mark ¼ and bake for 45 minutes. The cheesecake should wobble slightly in the centre.
Turn off the oven and leave the cheesecake in the oven for 1 hour, then remove from the oven and cool at room temperature. Cover and refrigerate. Serve decorated with lemon slices, mint sprigs and tiny flowers.