Start making sponge the day before baking bread. To make sponge, melt yeast in water and then mix in flour. Cover and let sponge rest for about at least 12 hours.
To make dough, dissolve the next portion of new yeast with water and mix the sponge with all of the remaining ingredients. Knead dough until springy. You might have to add some extra water if the dough is too hard. If this is the case, just add single 1 tablespoon (1 EL) portions of water slowly until dough is softer. Let dough rise.
Portion dough into 77 gram pieces and shape dough into buns. Put dough on parchment paper, if baking on a metal baking sheet or flour surface of a pizza stone. Slash rolls so they can release steam and won't explode while cooking. Leave dough on baking surface to rest for about 15 minutes in a warm place, covered with a towel.
Fill a baking pan with water and put in 200C (400F) oven on a shelf underneath the bread while cooking. The steam from the water will help give the bread a crunchy crust. Bake for 15 - 20 minutes if using baking sheet or 30 minutes if using pizza stone. Cook until bread is lightly browned.