Making the fondant:
After a few not quite right small scale trials and a bit of research we arrived at a recipe giving the right taste and consistency. We recommend practising on a smaller amount first as it's a bit tricky to get right!
Wipe the inside of a large saucepan with a very thin layer of butter. Put 3lbs of granulated sugar into the large saucepan and add 15 oz water. Mix and gently heat with stirring until the temperature reaches 107 ˚C. The mixture should be bubbling evenly across the entire surface at this point.
Add two 140g bottles of liquid glucose to the saucepan and gently mix in. Increase the heat and bring the temperature up to 115-118 ˚C.
Boil for 15min and then switch off the heat and allow the mixture to cool to about 45 ˚C without stirring. The mixture should be clear and become increasingly viscous as it cools.
Beat the clear mixture with a wooden spoon. Gradually it will begin to go white and become thicker. At this point, a small amount of water can be added to keep the consistency right, not too runny, not too thick. Add the vanilla flavouring at this stage too.
Allow the creamy white fondant to age over about 24 hours at room temperature in a sealed container.
Fill the two halves of the chocolate shell with the white fondant and place in the fridge overnight to chill and set slightly.
To the remaining fondant, add 3 drops of red food colouring and about 15 drops of yellow colouring and mix well.
Remove the chilled egg halves from the fridge and scoop out some of the white fondant from each centre.
Carefully drizzle in enough 'yolk' fondant to fill the holes and return just one half of the egg to the fridge overnight. The other half is kept at room temperature in a sealed container.
OK, time to put it all together. Melt about 25 g chocolate and carefully spread a layer, about 1/8" thick around the flat chocolate surface of the half egg (still in it's mould) which was kept at room temperature.
Quickly take the set half from the fridge and place it exactly on top of the other half and gently press the halves together. The fondant in the set half should be thick enough not to drip out when it is turned upside down.