Oh and another thing, I think adding cocoa and yoghurt makes it  taste weird (not to mention shelf life extending ingredients). The boza I drank in my childhood is just wheat flour (maybe millet), yeast, water and sugar. For instance, here you cannot find bread which tastes and feels like real bread because the large number of ingredients they put in it (see the garbage "Wonder Bread" as an example). The tastes adapt though and people love it. It's just enough to go on the street and watch people's waist lines and see the result of all these "wonder" products.

Miter,
Please post any proven recipe. Thanks! Geo