Thaw the phyllo pastry as per the instructions on the packaging. Unroll the sheets, cover with the plastic sheet provided and cover with a clean, damp tea towel. Preheat your oven to 160°C and grease the muffin pan.
Lay a single sheet of phyllo pastry on your work surface. Brush lightly with melted butter. Place another sheet of pastry on top. Repeat the process until you have used all 6 sheets.
Cut the phyllo stack into 12 pieces (4 x 3 strips). Press each piece gently into the muffin pan and bake for 20-25 minutes until golden and crispy. Set aside to cool while you make the custard.
To make the custard: whisk the eggs and sugar together for a minute until pale. Whisk in the cornflour.
Heat the milk and cinnamon sticks together in a small saucepan until the milk has just reached boiling point. Remove the cinnamon sticks.
Carefully pour half of the hot milk into the egg mixture while whisking. Then pour the egg and milk mixture back into the saucepan that has the remaining milk. Return the saucepan to the heat and stir for about 5 minutes, until the custard is thick and slightly darker in colour.
Remove the custard from the heat and whisk in the butter and vanilla extract. Leave to stand for 15 minutes, giving it a good whisk every 5 minutes. Spoon the custard into the phyllo cups and leave to cool and set.
For the topping: just before serving combine the castor sugar and cinnamon in a small bowl. Sprinkle about half a teaspoon of cinnamon sugar over one of the milk tart cups and give it a gentle shake to get the sugar into an even layer. Use a small creme brûlée torch to torch the sugar until golden and caramelised. Repeat with the remaining cups. Serve immediately.