200 g chilled unsalted butter, chopped into small pieces
250 g plain flour
1/2 cup (125 ml) sour cream
1 × quantity sour-cream pastry (see pastry ingredients and method)
1/3 cup (80 ml) lemon juice
grated rind of 1 lemon
150 g castor sugar
600 ml cream
9 egg yolks (from large, fresh free-range eggs)
icing sugar (optional), to serve
Put the butter and flour into the bowl of a food processor, then pulse until the mixture resembles coarse breadcrumbs.
Add the sour cream and pulse again until the dough just forms a ball.
Carefully wrap the dough in plastic film and leave to rest in the refrigerator for 15–20 minutes.
Roll out the dough until it is 5 mm thick, then use it to line a 20 cm tart tin with a removable base. Chill the pastry case for 20 minutes.
To blind bake, preheat the oven to 200°C. Line the pastry case with foil, then cover with pastry weights. Blind bake the pastry case for 15 minutes, then remove the foil and pastry weights and bake for another 5 minutes. Leave to chill.
Roll out the chilled dough and use to line a 20 cm flan tin with a removable base. Chill the pastry case for 20 minutes.
Preheat the oven to 200°C. Line the chilled pastry case with foil and pastry weights and blind bake for 15 minutes. Remove the foil and weights and bake for another 5 minutes.
Reduce the oven temperature to 180°C.
Meanwhile, beat the sugar, egg yolks, lemon juice and rind until smooth, then fold in the cream.
Fill the warm pastry case with the lemon mixture, taking care not to overfill it. Bake until the filling is set around the edges but still wobbly in the middle (this will take anywhere from 25–45 minutes, depending on your oven).
Remove the tart from the oven and set aside to cool to room temperature to allow the filling to set completely – it should be the consistency of a very ripe brie, yet firm enough to cut into portions.
Refrigerate for an hour or so if necessary to help set the filling. Serve dusted with icing sugar.