Preheat the oven for 200 degrees Celsius.
Melt the butter, and set aside.
Roll out the puff pastry down to 5mm thick, if necessary. Butter the pastry with the melted butter, roll it up like a snail. Leave the pastry to chill for 10 minutes to set the butter. Cut the pastry into 1cm disks, roll out each disks into thin rounds. Line muffin tins with the puff pastry. Push it down with a rolling pin and line flush against the sides.
In a saucepan, bring milk to the boil. Add sugar and egg yolks in a bowl and whisk till pale. Add hot milk to egg mix small amount at a time. Sift the flour in egg mixture and mix well.
Zest Lemon and keep aside.
Add back to saucepan and thicken till dropping consistency from the back of your spoon is firm. Add lemon zest and cinnamon in mix. Spoon mix into puff pastry moulds and bake in the oven for 16-20 minutes until puff pastry turns golden brown.
«There are many various flavours that can be used instead of lemon zest. Maybe add vanilla seeds, orange zest etc. »