Measure the flour into a bowl and make a well in it. Crumble in the fresh yeast/sprinkle in the powdered yeast. If you are using dry yeast you need to "proof it" by pouring 100 g of your water over it and waiting for 15 minutes or so, until it is foaming. If you are using fresh or instant yeast, you can omit that step.
Sprinkle on the salt, pour on the water and incorporate all of the ingredients in your bowl. Turn the dough out onto your work surface and knead for five minutes.
Add the mash and the rosemary and knead for a further ten minutes. The dough will get very sticky and slack. Don't give up, just use a scraper to continue to gather it all up and get it off your hands and keep going.
Scrape it all up and pop it back in the bowl. Let it rest for 1-2 hours.
Pull the dough out and divide it into four blobs. Flour your hands (try to avoid flouring the work surface) and shape each blob into a tight round ball. Alternatively, form each blob into a sausage and pop each sausage into a baking tin that is well greased.
If you have made balls, place each ball on a well floured tea towel, sprinkle each ball with flour and cover with another tea towel. If you have put in tins, cover the tins with a tea towel.
Let rest for 1 hour.
Preheat oven to 200 degrees C (400 degrees F). If you are baking in a ball shape, transfer each ball on to a baking tray that is lined with baking parchment. Put the tray (or the tins) in the oven and bake for 45 minutes.
Remove from the oven and let cool completely before cutting.