If using store-bought pastry, unroll and keep it very cold.

Roll the pastry into a tight cylinder (“spiral” technique), then slice into discs.

Press each disc into a lightly greased tartlet mould, letting the edges rise slightly.

In a small pan, combine 120 g sugar and 100 ml water. Add the cinnamon stick and lemon zest.

Bring to a boil, simmer 2 minutes, then remove from heat and infuse 10–15 minutes.

Strain to obtain a clear syrup.

Whisk egg yolks with flour until smooth.

Heat milk with vanilla (if using) without boiling.

Gradually add hot milk to yolks to temper them, then return to pan.

Cook over low heat, stirring constantly until thickened.

Gradually add filtered syrup to adjust sweetness and flavour. Let cool slightly.

Preheat oven to maximum heat (250–300 °C / 480–570 °F).

Fill each pastry with warm custard, leaving 2–3 mm under the rim.

Bake 8–12 minutes, until the surface has dark brown spots.

Let tarts cool a few minutes before removing from moulds.

Serve warm, optionally dusted with cinnamon or icing sugar.