Heat the oven to 180C/fan 160C/gas 4. Whizz the biscuits to fine crumbs in a food processor, pour in the butter then whizz again. Press into the base of a 20cm springform tin and bake for 5 minutes. Cool.
Beat together the soft cheese with the flour, honey, vanilla, whole eggs, yolk and soured cream until smooth. Put the tin on a baking tray and pour in the filling.
Bake for 40 minutes and then check – it should be set but wobbly in the centre. Leave in the tin to cool completely (if you can, leave it in the switched-off oven for an hour to cool first, with the oven door open a little. This means it shouldn’t crack on top).
To make the salted honey topping, put the honey, 1 tbsp water and a few drops of lemon juice in a metallic pan so you can see the colour change. Stir well, then put on a low-medium heat and keep stirring until tiny bubbles begin to form. Stop stirring, but keep cooking and swirling the pan until the honey turns a nutty golden brown and smells caramelised. Take off the heat and stir in the 2 tbsp double cream. It might splutter a little so be careful. Stir in the salt and cool.
Once the cheesecake has cooled to room temperature, leave in the tin, spread the soured cream on top and chill completely for a couple of hours.
Serve with the salted honey spooned over the top of the cheesecake.