Melt A till smooth. (use a microwave or a double boiler).
Whisk B till pale and add to the cream cheese batter. Keep this cake batter aside.
Beat egg whites until foamy and alternately whisk in sugar and cornflour until soft peaks form.
Add and stir in a big dollop of the egg whites into the cake batter.
Fold in the rest gently until combined.
Grease an 8 inch cheesecake tin with butter and flour the surface. Tap out the excess flour. Cover the bottom of the cake tin with foil to prevent water seeping through.
Pour the cake batter into the tin and sit it in a larger baking dish filled with boiling water.
Make sure the water is approximately ¾ of the cake height. Bake in a preheated 150 degrees oven. When the top is nice and golden, reduce the temperature to 125 degrees and bake for another 45-60 minutes.
Notes
Remove cake from oven to cool for approximately an hour before removing it from the tin.