I used my own recipe but the idea comes from diamondsfordessert.com

For Lion Cookies you need:

50g butter
1 egg
100g sugar
1 package of vanilla sugar
250g flour
0.5 teaspoon of baking powder

Mix all the ingredients together and knead the dough. Put half of the dough into an other bowl and continue to add following ingredients:

100g chocolate (melt it in a bain-marie before adding)
25 g black cocoa powder

Form the vanilla dough like a sausage and roll out chocolate dough about 1~2 cm thick. Wrap the chocolate dough around the vanilla sausage dough.
Here is a good example from diamondsfordessert.com:

Afterwards, wrap the Lion Cookie dough in a foil and leave it chilled for 15~20 minutes. Then slice the chilled dough and bake the cookies for about 15 minutes.

oven baking temperature: 180 C°
baking time: ~15min

It looked so easy at first, but it was quite a hard challenge! Firstly the cookie dough stucked and while I was slicing the dough it was falling to pieces! May I should give it a second try someday.