Hazelnut - when and how to prune?

hallo,

have found similar threads but none tell me how and when to prune a hazelnut? Last year i did not prune at all thinking the nuts will come at the end of new shoots -- very few did. They are now getting to be rather large bushes with several leaders. I have not fed them and still they produced more leaves than nuts --- so do i prune them now in autumn or next spring / do i prune them at all, just cut them back to a smaller size, etc? And if i have to prune them, how far back can i go -- several nodes from junction of older branch, etc? No idea what to do.

thanks for help, karaman