Peel the potatoes, cut into very fine cubes and mix with the chopped rosemary. Finely dice the onion as well.
Heat the stock in a separate saucepan.
Heat the butter and oil and fry the rosemary potatoes with the bacon and diced onions. Add the rice and cook until translucent while stirring. Deglaze with a dash of white wine and stir until it has evaporated. Then gradually add the hot stock so that the rice is always just covered with liquid.
The risotto should have a creamy consistency and the rice grains should still have a bit of bite.
Finally stir the freshly grated parmesan into the risotto and season with black pepper.