It was probably some form of chleb żytni razowy (wholegrain rye). There are dense, heavy breads in Poland baked in long squarish loaves, stretches of which are cut off and sold by weight. The recipe would probably be a very involved several-day procedure uisng sour-dough starter, extensive kneading, rising, re-kneading and in the end it could be a flop after all that effort. Polish bread ovens (piec chlebowy) have just the right heat, humidity and ventilation required, and these are nearly impossible to reproduce at home. But hunt about on the net. In English they may call it whole rye, whole-grain rye or maybe even just black bread. POWODZENIA - GOOD LUCK!
