Roll out the pastry to approx. 3 cm thick and cut into 12 squares (see tip). Place the pastry squares into the wells of the prepared tin, prick the bases.
Mix the cheese, potatoes and courgette in a bowl, add the flour and all the other ingredients up to and including the nutmeg, mix well. Divide the mixture onto the pastry bases.
Approx. 30 mins. in the lower half of an oven preheated to 220°C.
Mix the chives with the sour single cream. Serve with the tartlets.