Mix the flour, sugar, lemon zest and salt in a bowl. Add the butter and rub together using your hands to form an even, crumbly mixture. Add the egg, mix quickly to form a soft dough – do not knead. Flatten the dough, cover and chill for approx. 30 mins.
Raspberry puree filling
Purée the raspberries with the cranberry juice, press through a sieve into a pan. Stir in the agar-agar using a wire whip, bring to the boil while still stirring, boil fast for approx. 2 mins, stirring constantly. Remove the pan from the heat, stir in the reserved lemon juice, allow to cool a little, then refrigerate.
To roll out the pastry
On a lightly floured surface, roll out the pastry to approx. 4 mm thick. Cut out circles (each approx. 12 cm in diameter), place in the prepared tins. Prick the pastry bases firmly with a fork.
To blind bake
Approx. 15 mins. in the lower half of an oven preheated to 200°C. Remove from the oven, allow to cool a little, remove from the tins and leave to cool on a rack.
To prepare the tarts
Stir the raspberry puree until smooth, pour into the tart bases. Whip the cream until stiff, spoon into a piping bag with a smooth nozzle (approx. 6 mm in diameter). Pipe the cream on top of the raspberry puree, garnish with raspberries, pistachios and peppermint, dust with icing sugar.