Everyone seems to be in un-perfect agreement as to what a Kolache is or isn't .. I know Kolaches to be nice little round nests approx. 3 (+) inches across, and filled with 4 Traditional fillings, Poppyseed, Apricot, Cottage Cheese, and Prune .. These 4 filings are those I call Traditional, at least in the sense that they were always the ones used by my Grandmother, Agnes ( Spousta ) Wanek. Her family as well as my Grandfathers came here to the USA from Bohemia, ie: The Austro-Hungarian Empire, and always referred to themselves ( as we do still ) Bohemians.
Her Kolache dough recipe is very similar to those I have seen above, so no real need to add it here. There is one major difference however in the Poppyseed filling recipe's I have found listed here, at least one that qualifies as major to me .. The Poppyseeds should ALWAYS be ground. Also, while you can use Milk for the liquid in making the filling, it is preferable to use the Prune juice which you get from stewing the Prunes for that filling. It makes for a much richer Poppyseed filling.
Poppyseed grinders can easily be found by typing the word into your search bar.
All Poppyseed fillings that I am aware of from Central Europe ( Czech, Slovak, Hungarian, and Austrian ) are all ground.