Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente.

While the pasta cooks, heat a little oil in a pan over medium heat. Add the sliced sausages and cook until browned and cooked through, about 5-7 minutes. Remove sausages from the pan and set aside, leaving any rendered fat in the pan.

If using optional onion, add it to the pan and cook until softened, about 3-4 minutes. If using optional garlic, add it in the last minute and cook until fragrant.

Add the butter to the pan and let it melt. Return the cooked sausages to the pan.

Drain the cooked pasta, reserving about 1/2 cup of the starchy pasta water. Add the drained pasta to the pan with the sausages and butter mixture.

Add the grated cheese to the pan. Stir everything together, adding a little reserved pasta water as needed to create a light sauce that coats the pasta and sausages.

Season with salt and pepper to taste. Serve immediately, garnished with optional fresh herbs if desired.