First, make the leaven. Dissolve the yeast in the lukewarm milk (not hot) and add a bit of flour so that you have a batter. Let it rise covered with plastic wrap (about 1 hour). 

Beat the melted butter with the sugar until they are well integrated. Add the eggs and all the liquids and mix. 

Finally add the leaven, the mahlab and start adding flour mixing and kneading by hand (not too much kneading). Let it rest until it doubles. 

Divide into pieces and form the tsourekia, place on baking paper, and when they rise once more bake at 170°C, both radiant elements until they are golden brown (30-40 minutes). If you press the dough with your finger, the mark should disappear and not leave a hole.

Let them cool in the baking tray. 

If you like, brush them with egg yolk before you bake them or cover them with chocolate icing after they cool properly. 

Chocolate icingMelt the chocolate with the mil. Remove from heat and add the butter, stirring so that it melts, add the egg yolk and stir quickly so that it doesn't cook. This particular icing firms in a few hours but remains soft. If you melt white chocolate you can make decoarations.