Line the bottom of an 6" square cake pan or a 7" round cake pan with parchment paper. Set aside.

If making cheesecake with a pastry base, set the oven to 180C/350F/Gas 4.

If making cheesecake with a biscuit base, set the oven to 200C/400F/Gas 6.

To make a pastry base: Place the flour, margarine, and pinch of salt into a mixing bowl and add enough cold water to bring to a dough. Wrap dough in plastic wrap and place in the fridge for 30 minutes before rolling into a circle to cover the base of the pan.

Line the pastry base with a piece of parchment paper and a layer of baking beans. Bake blind at 180C/350F/Gas 4 for 15-20 minutes until just cooked. Remove from oven and set aside to cool. Remove the baking beans and parchment.

Increase oven to 200C/400F/Gas 6 to bake the cheesecake filling.

To make a biscuit base: Place the biscuit crumbs and melted butter in a mixing bowl and mix until they combine and stick together. Pour into the cake pan and spread evenly, pressing down with the back of a spoon. Place in the fridge while you prepare the filling.

To make the filling: Place the eggs whites in a clean, grease-free bowl and whisk to stiff peaks. Set aside.

Place the egg yolks into a bowl with the sugar and beat together till combined. Beat in the softened margarine. Set aside.

Place the mascarpone, flour, and milk into a large mixing bowl and beat to combine.

Add the sugar mixture to the mascarpone mixture and mix well to combine.

Stir in the lemon zest and a little lemon juice to personal taste.

Stir in sultanas if using.

Gently fold in the stiff egg whites.

Pour filling over cheesecake base and place in the oven at 200C/400F/Gas 6 for 10 minutes.

Reduce oven temperature to 180C/350F/Gas 4 for 30 minutes or until set and golden on top, turning the pan halfway through cooking.

Allow cheesecake to cool before cutting to serve.

Store in the fridge for 2-3 days.

Cheesecake can be frozen, cover it with parchment paper then wrap in kitchen foil and place in the freezer. You can freeze the whole cheesecake, or cut portions.

Defrost in the fridge before eating.