Whisk together ¼ of the milk and the flour in a large bowl.
Bring the sugar, lemon juice, water and cinnamon to a boil in a small saucepan, and simmer for 3 minutes. Do not stir.
Heat the remaining milk, do not simmer and whisk slowly into the flour mixture. Remove the cinnamon from the sugar syrup and slowly add to the milk mixture, whisking continuously. Whisk in the vanilla and egg yolks. Set aside to cool.
Roll the pastry lengthways and cut the pastry roll into 12. Using a rolling pin press down on the scrolled side and shape it into a circular disc. Use these to line a muffin tin.
Pour the cooled custard into the pastry tarts and bake in the preheated oven for 15 – 20 minutes or until the pastry is cooked and custard set.
Remove from and oven and allow to cool. Sprinkle with icing sugar, and a dusting of cinnamon and serve.