300g plain flour, plus extra for dusting
240g cold unsalted butter, diced
½ tsp salt
150g soured cream

Mix together the flour, butter and salt, and work to a fine crumb by hand or in a food processor. Add the soured cream and work just until the pastry comes together; it can be quite soft. Smooth out the dough with a little flour, flatten to a thick disc, cover with clingfilm and chill for at least an hour.