Keep the broth at a very slow, steady simmer near the risotto pot.
In a broad, sturdy pot over medium-high heat, cook onion in 1 tbsp butter and the oil until translucent. Add sausage slices and cook until browned well on both sides. Add the wine and stir from time to time until the wine has bubbled away completely.
Add rice and stir until the grains are coated.
Add 1/2 cup (120 ml) simmering broth and continue cooking as for basic risotto, adding broth as needed.
Finish cooking with broth, or with water if the broth runs out. Cook until rice is tender but firm, with no liquid remaining in the pot.
Off heat, stir in pepper, remaining butter, and all the Parmesan until melted and clinging. Taste and correct for salt. Serve promptly.