Cottage cheese flan
Preheat the oven to 200°C/400°F/Gas Mark 6. Grease a 20cm/8in tart tin with a little butter.
Put the flour and a pinch of salt on a work surface. Make a well in the centre, and pour in the 2 beaten eggs and 150ml/5fl oz of the sour cream. Add 175g/6oz of the butter, cut into pieces, and work into a smooth dough with your hands. Knead for 10 minutes. Cover the dough with a cloth, and leave in a cool place for 1 hour.
Mix the cottage cheese with the remaining butter, egg yolks, dill and salt to taste. In a separate bowl, whisk the egg whites until stiff, then fold into the cottage cheese mixture.
Line the prepared tart tin with the pastry. Trim the edges, and spread the cottage cheese mixture evenly over the bottom of the pastry.
Brush the top of the mixture with the remaining sour cream, and bake in the oven for 30 minutes or until the filling is set. Serve hot.