Preheat the oven to 150ºC/300ºF/Gas mark 2

In a small saucepan, melt the butter

In a food processor, add the Hobnobs and grind to a fine crumb

Add the ground biscuits to the butter and combine

Empty the mixture into the base of the tin and smooth the surface evenly using the back of a tablespoon

Bake the base for about 15 minutes then set aside to cool while you make the cake mixture

Zest & juice the lemons. Set aside

In the food processor you used to crumb the biscuit, add half the blueberries and lemon juice and purée

In a stand mixer (or large mixing bowl if doing it by hand) add the cream cheese, sour cream and sugar and mix thoroughly

Gently whisk the eggs in a measuring jug before adding them to the cheese mixture in 3 stages, mixing well after each addition

Add the puréed blueberry & lemon juice mixture followed by the lemon zest, making sure it's well incorporated

Boil a kettleful of water

Before pouring the cheesecake mixture into the tin, wrap the tin in foil to make it water tight

Put the tin into an oven tray (at least 5cm/1-inch deep)

Pour the cheesecake mixture into the tin and put the oven tray & cake into the preheated oven

Fill the oven tray to about ½cm/¼-inch below the rim with the boiled water

Bake for 1 hour 15 minutes

When cooked, turn off the oven and allow the cheesecake to cool in the oven, with the door ajar

When completely cool, top with the other half of the blueberries and put in the fridge