1tbspcornflour/corn starch mixed with 1 tbsp water
Pre-heat the oven to 230ºC and grease a 20cm springform cake pan well.
For the crust, combine the crushed cookies with the melted butter and mix well. Press into the bottom and up the sides of the prepared cake pan. The crust doesn't have to be all the way up to the top of the pan.
Place in the freezer for 15 minutes.
To make the cheesecake filling, beat the cream cheese and cottage cheese until fluffy. Add the sugar and flour and continue beating until well mixed, scraping down half way through the mixing.
Add the eggs and yolk, one at a time, scraping down the bowl with a rubber spatula after each addition.
Stir in the sour cream, lemon zest and vanilla extract.
Pour the filling onto the chilled crust and place on a baking sheet (if your oven's temperature is not steady and you know it has heat spots, wrap the bottom of the cake pan in foil and place the cake pan into a deep roasting dish. Fill up to half way up the cake pan's height with boiling water then place in the oven.) and place in the oven.
Bake for 15 minutes at 230ºC then turn down the heat to 110ºC and allow to bake for a further 45-60 minutes, until the cake's centre jiggles slightly when the pan is gently shaken.
Mix together the sour cream and sugar and pour gently on top of the cake and return to the oven to bake for another 15 minutes.
When the cheesecake is baked, switch off the oven and open the oven door. Allow the cheesecake to cool for at least one hour this way and then transfer to the fridge to cool overnight.
To make the sauce, combine all the ingredients in a small saucepan and simmer for 5-10 minutes until the sauce has thickened slightly. Cool to room temperature and serve with slices of cheesecake. e