Heat blueberry jam ingredients in a saucepan until berries burst and mixture thickens.
Strain the jam through a sieve and leave to cool completely.
Rub butter into flour until crumbly, stir in sugar, then cut in the egg to form a dough ball.
Wrap pastry in film and chill for at least 30 minutes.
Roll out pastry to 3mm thickness on greaseproof paper and cut 12 circles with a 5cm cutter.
Place pastry circles in a greased muffin tin and press 1cm x 18cm strips around the sides.
Chill the lined tin for 15 minutes and preheat the oven to 170°C.
Beat frangipane ingredients together until smooth.
Prick pastry bases, add 2.5ml of jam to each, and top with frangipane.
Bake for 25 minutes until golden, then cool on a wire rack.
Mix icing sugar with water to a thick paste, spread over cooled tarts, and top with fresh blueberries.