finally I managed to post this simple but fun tutorial. We used it for Nicky's Birthday Party Favours and it was a success.
So from now on, recycle your old crayons and give them a fun new life. Even if you have small parts, you can mix and match them to have great results. We did some girly and some just for boys but none turned out boring.
A note on this part: you can use the oven or the microwave if you are in a hurry. Please never leave them unattended as they can over-melt, creating not only a mess (spillage hard to clean) but also bubbles on the surface (and this is not that nice on the final result)
Be careful when extracting as it's very hot. ONLY adults should do it.