Roll out the pastry on a surface lightly dusted with the Parmesan to about the thickness of a ten-pence piece. Stamp out 12 rounds using a 6cm plain cutter and line a shallow 12-hole bun tin. Chill for 20 minutes. Preheat the oven to fan 180C/conventional 200C/gas 6.
Prick each pastry base with a fork and bake for 15-20 minutes until golden. Remove from the tin and leave to cool on a wire rack. Meanwhile, tear the leaves from the parsley stalks and put all but 12 of the small sprigs in a food processor with the pine nuts, then whizz until coarsely chopped. Then add the feta, garlic and oil and whizz to make a thick paste. Keep the reserved sprigs in a bowl of water in the fridge. The pastry bases will keep in a tin for up to 2 days and the pesto will keep in the fridge overnight.
To serve, dollop a spoonful of the feta pesto onto the tarts and top each one with two cherry tomato halves. Garnish with the reserved parsley sprigs. Arrange on a platter and hand round with a bowl of black olives and sparkling mint & lemon juleps.