Whisk butter, icing sugar and vanilla.
Mix in egg and egg yolk one by one.
Sieve flour and starch in and mix.
Put dough in pipping bag with a small smooth nozzle. Pipe on a baking tray. (with baking paper)
Bake in preheated oven at 180° C for 9 minutes.
When the biscuits have cooled down, melt chocolate and coconut oil (bain marie), dip both ends of biscuits in chocolate.