For the fondant, in a medium bowl whisk together the golden syrup, butter, sugar, salt and vanilla until well combined. Place a quarter of the mixture in a small bowl and mix in a tiny amount of food colouring, bit by bit, until you reach the desired colour of an egg yolk. Refrigerate both mixtures for 30 minutes.
For the coating, melt and temper the chocolate. Fill the egg moulds with the melted chocolate, following the technique for moulded chocolates and saving any excess chocolate. Leave to set, then fill the egg moulds once more to give a nice thick shell of chocolate. Leave to set again, then remove the chocolate shells from the moulds. Each chocolate mould will make half an Easter egg shell.
Remove the fondant mixtures from the fridge. Spoon the white and yellow mixtures into 2 separate piping bags with the ends snipped off. Pipe the white fondant into 6 of the chocolate moulds, filling them to about three quarters of the way up.
Pipe a blob of the yellow mixture into one half of each mould. Using a hot knife or spatula, warm the surface of a mould, then place another mould on top to seal and make a complete Easter egg shell. Repeat with the remaining moulds.
Recipe from Chocolate by Molly Bakes (£20, Square Peg)