Finely chop the dark couverture chocolate and set aside 150g to use as a seed.

Melt the remaining 350g of chocolate in a double boiler over simmering water until it reaches exactly 45-50°C (113-122°F).

Remove the chocolate from the heat and gradually stir in the reserved 150g of seed chocolate to initiate crystallization.

Continue stirring until the temperature drops to 27°C (81°F) for dark chocolate.

Briefly return the bowl to the heat for 5-10 seconds at a time until the working temperature of 31-32°C (88-90°F) is achieved.

Polish the interior of polycarbonate egg molds with a clean cotton ball to ensure a high-gloss finish and easy release.

Fill the molds completely with tempered chocolate, tap firmly on the counter to remove air bubbles, then invert over a bowl to pour out excess, leaving a 2-3mm shell.

Scrape the mold surface clean with a bench scraper and refrigerate for 20 minutes until the chocolate has contracted and released from the mold.

Gently unmold the shells and join two halves by briefly pressing the rims against a warmed baking sheet before pressing them together to fuse.

Pipe melted white chocolate patterns onto the exterior for traditional Easter decoration.