waw ...reminds me old times ...
I am vegeterian now ...actualy pescaterian ...but in my childhood my mom made a lot of those and yes you dip them in vinegar and it is awesome

now my mom makes varieniki that is similar ...i think the dow is the same but it has potato with fried onion inside ..or it can be done with cheese ...or some other times with cherry

so nice ...i will ask my mom to make me some as soon as i see here.

btw it is a hell a lot of work to make them ..but they taste really good
:)