Heat the oven to 180°C/350°F/gas mark 4. Line a baking tray with parchment.
Make a hole in the centre of the top of each croissant with a small knife. Wiggle a clean finger around in the hole to make room then dip the whole croissant briefly in the syrup and place on the tray. Pipe 50g (2 oz) of frangipane into each hole.