In a bowl, whisk water, milk and sugar with the crumbled yeast until smooth, about 20 seconds. In a mixing bowl, combine flours, skim milk powder and salt.
Press a well in the center and pour yeast mixture into it. Dust with a little flour from the edges and let rest for 10 minutes. Add yogurt and knead everything for 5 minutes.
The dough will be soft.
Line a baking sheet with baking paper.
Slide the dough onto a floured work surface. Using 2 large tablespoons moistened with water, divide 9 equal-sized pieces and place them on the baking sheet, spacing them apart.
Dust rolls with a little flour.
Preheat oven to 210 °C top/bottom heat.
Place roll tray in the middle of the oven and bake for 10 minutes. Then reduce heat to 175 °C and finish baking for approx. 15 – 20 minutes.
Let rolls cool slightly on a rack before cutting. Completely cooled rolls can be frozen. To do this, wrap each roll individually in plastic wrap and then place rolls in a freezer bag.
Buns can be removed individually. Wrap in plastic wrap and allow to thaw overnight at room temperature and next day n. Bake/toast briefly the next day.