Some more pieces of information on medieval and early modern helva gatherings of turkish guilds:
The Fütüvvet-nāme-i kebīr. A Manual on Turkish Guilds
Author(s): D. A. Breebaart
Source: Journal of the Economic and Social History of the Orient, Vol. 15, No. 1/2 (Jun.,
1972), pp. 203-215
If your library has access to jstor, you will find it there.
E.