Belated cheesecake recipe

I know I promised ages ago. What can I say? I'm a slacker.

When I was a kid, my mom made the best cheesecake (still does, I'm sure) which we always called Judy Wollstadt's cheesecake, presumably because my mom got the recipe from Judy, a college friend. A while back, I found a similar recipe (not quite the same) in one of my magazines, which was good, as I'd lost my copy of Judy Wollstadt's cheesecake recipe and anyway, this one is in UK measurements and products. The main difference is the addition of lemon and the fact that some sour cream is in the filling as well as the topping. Pretty close, though, and every bit as tasty.

Not Quite Judy Wollstadt's Cheesecake

For the crust:
85g/3oz butter, melted
10 digestive biscuits (140g/5oz) made into fine crumbs
1 tbsp granulated or golden caster sugar

For the cheesecake filling:
3x300g packs full-fat soft cheese (e.g. Philadelphia), at room temp
250g/9oz golden caster sugar
3 tbsp plain flour
1 1/2 tsp vanilla extract
finely grated zest of 1 lemon
1 1/2 tsp lemon juice
3 large eggs, plus one yolk
284ml sour cream

For the soured cream topping:
142ml carton soured cream
1 tbsp golden caster sugar
2tsp lemon juice

Preheat the oven to 180C (160 fan)/gas 4.

Combine crust items and press into the bottom of a 23cm springform pan. Bake for 10 minutes; cool on a rack while preparing filling.

Increase oven temp to 240/200/gas 9.

Beat cheese until creamy, then gradually add sugar, flour, a pinch of salt, vanilla, lemon zest and juice. Then whisk eggs & yolk in one at a time, being sure to scrape bowl sides. Measure out 200ml of sour cream from large container and add to cheese mixture; reserve rest for topping. The batter should be smooth, light and somewhat airy.

Pour filling over crust. Bake for 10 minutes; reduce oven temp to 110/90/gas 1/4 and bake for 25 minutes more. If you gently shake the tin, theh filling should have a slight wobble. Turn off oven and let cake cool in oven for 2 hours. For a cake that's creamy in the centre, open door slightly; for a drier texture, leave it closed. A slight crack in the top is normal during cooling.

Combine the reserved sour cream with the rest of the topping ingredients and spread over the cheesecake. Cover loosely with foil and refrigerate at least 8 hours or overnight.