First up, make the custard. Add the plain flour and milk into a saucepan then use a whisk to beat it until smooth.
Cook over a medium heat, whisking often until it thickens. Once thickened, take it off the heat.
Beat in the egg yolks and vanilla bean paste. Set it aside.
In another saucepan, add the water, golden caster sugar and cinnamon stick. Cook over a medium-high heat until it reaches boiling point.
Remove the cinnamon stick, then slowly pour the sugar syrup into the egg/milk mixture whilst continuously beating with a whisk. Leave it to cool down.
Preheat the oven to 290℃ (or as high as it goes)
Fold the sheet of puff pastry in half, then roll it up tightly from the short end.
Cut it into 12 equal sized portions. Place the rounds into each hole of a muffin tin. Leave it for a few minutes to warm up so it is easier to mould.
Wet your fingers and thumbs with cold water and press each piece of pastry into the muffin tin holes. Smooth the dough up the sides. This may take a bit of patience.
Pour the cooled custard 3/4 of the way up each pastry case.
Bake for 8-9 minutes (this may be longer if your oven is set at a lower temperature) or until the shells are golden and crisp and the tops are blackened in spots. If baking at 220℃, they should take approximately 20 minutes. If you can go as high as 250℃ then 15 minutes should be enough.
Leave to cool slightly before sprinkling with icing sugar and ground cinnamon. They are best eaten whilst still warm.