Amazingly moist and just the right amount of density! I cut the ingredients in half because all I had was one 10x10. Used 125 grams (a little over 1/2 cup) butter, since butter often comes in 250 gram blocks in Czech. and I just cut it in half. I also used 2 eggs and added one tablespoon of veggie oil since there were some comments about moistness. I also added a bit more sugar (less than 1/4 cup) because I forgot and added the sugar in with the flour mixture rather than with the butter as instructed, so I used it to help whip the butter. In my opinion it needed that extra sugar to be a little more sweet. I also don't have an electric beater yet so I let the butter reach room temperature and whipped it with a fork, it's hard work but it turns out just fine! I had some instant chocolate frosting and swirled it into the batter before baking, it came out perfect!