To begin, separate the egg yolks from the whites carefully, ensuring no trace of white remains. Pass the yolks through a fine sieve into a bowl to remove membranes for a smoother texture. Transition to making the syrup.

In a small saucepan, combine caster sugar, water, and a pinch of salt. Heat gently over medium heat until the sugar dissolves completely, then bring to a steady simmer without stirring. Continue until it reaches a thread stage (around 105°C). Move to incorporating the yolks.

Slowly pour a ladle of the hot syrup into the beaten yolks while whisking continuously to prevent curdling. This gradual heating prepares the yolks for cooking. Transition to cooking the mixture fully.

Return the tempered yolks and remaining syrup to the saucepan. Stir constantly over very low heat with a wooden spoon until thickened to a custard like consistency. Avoid boiling to maintain a bright yellow colour. Move to cooling.

Transfer the cooked mixture to a clean bowl. Cover with cling film directly touching the surface to prevent a skin from forming. Let it cool completely before filling the shells.

If using traditional rice paper shapes, cut and mould them while slightly damp so they become pliable. These will be the casing for the ovos moles. Move to assembling.

Spoon the cooled yolk filling into each rice paper shell, sealing edges by lightly pressing with damp fingers. Work gently to avoid tearing. Transition to finishing touches.

Serve immediately for the freshest taste or store in an airtight container for up to 3 days. Presentation tip: Arrange in small paper cases or a decorative tin to evoke the traditional Aveiro style.