From Classic German Baking.
Fresh yeast gives these rolls a bit of added moisture, oven spring, and flavor, so I prefer to use it here, but instant yeast can also be substituted. One more thing to note: The larger amount of butter, folded and rolled together with the yeasted dough to create all those flaky layers, must be in one block before using. If you can find that amount of butter in one block, you're good to go. If your butter consists of several pieces, let them soften, knead them together until cohesive, and chill until cold and firm. —Luisa Weiss