warm cooked
beets,,
you need to add finely chopped onion and some sugar - you boil beetroots first (I guess in well salted water), then you grate'em, add chopped onion, sugar and black pepper to taste and fry it on cooking oil in a covered pan until the taste of onion permeates the whole dish (don't add too much sugar though) there should be quite a lot of onion
as for warm beetroots with horseradish - I don't know - ćwikła z chrzanem is usually served cool
I've forgotten about vinegar - you need to add some vinegar - but not really much - I would start with half a table spoon - my mom always used clear white vinegar (ocet spirytusowy - the cheapest stuff in POland) - I think aromatic vinegars will spoil the dish as it's taste is pretty subtle - maybe a plain white wine vinegar would be all right - I don't know
I've forgotten about vinegar - you need to add some vinegar - but not really much
oh, well - you could use lemon juice or citric acid instead of vinegar too - maybe it's even actually tastier then