Stew of new potatoes in white wine, with mortadella and mozzarella

Mortadella is a finely hashed/ground heat-cured pork sausage with lard pieces, delicately flavored with garlic and anise seed and optionally with broken pieces of pistachio. Traditionally the pork filling was ground to a paste using a large mortar (mortaio) and pestle. Mortadella originated in Bologna la Grassa, the "fat" city overflowing with bounty, though it is made elsewhere in Italy, and a similar commercial product, called "bologna" often omitting the lard.
Of course it has been impossible for me to find mortadella in Devon! This has been sent to me by my dearest friend Terry directly from Italy. You could substitute it with a few slices of a good ham. Terry also sent me this recipe and of course I couldn't resist trying it straight away! Thank you Terry!

Ingredients: 500gr new potatoes, 70gr scallions, 2 garlic cloves, 1 Tbsp butter, 2 Tbsp olive oil, 1 glass and a half of dry white whine, 1 small branch of rosemary (fresh or dry), 70gr mortadella, 125gr mozzarella, salt, pepper

Wash the new potatoes well without peeling them. Peel the scallions and cut a couple only, leave the others whole. Peel the garlic and cut it into small stripes. Warm up butter and oil in a large pan, add scallions and garlic and fry for a few minutes without letting the garlic burn, then add new potatoes, fry again for a few and adjust with salt and pepper. Add rosemary, mix well and pour 1 glass of white wine first. Cover and stew for about 30 minutes checking now and then that it doesn't need more wine. Cut the mozzarella into small cubes and the mortadella into stripes. Add them to the new potatoes, toss covered for about 2 minutes until the mozzarella melts. Serve warm guarnished with more rosemary.