In a medium bowl, combine the fresh bread crumbs, lightly beaten eggs, Parmesan cheese, parsley, and minced onion.
Season generously with salt and pepper.
Mix until well combined and let the mixture rest for 10 minutes to allow the bread crumbs to hydrate.
Using your hands, roll the mixture into small, uniform balls, about 1/2-inch in diameter.
Place them on a plate or baking sheet. You can refrigerate them at this point until you are ready to cook.
Bring a large pot of salted water to a rolling boil. Gently drop the nudi into the water.
Cook until they float to the surface, which should take about 3-4 minutes.
Remove them with a slotted spoon and set aside, keeping them warm.
In the same pot of boiling water, cook your pasta according to package directions until al dente.
While the pasta cooks, melt the butter in a large skillet over medium heat.
Add the fresh sage leaves and cook, swirling the pan occasionally, until the butter foams, turns a nutty golden-brown, and the sage leaves are crispy. This will take about 5 minutes.
Drain the pasta, making sure to reserve about 1 cup (240 ml) of the starchy cooking water.
Add the drained pasta directly to the skillet with the brown butter sauce.
Toss to coat, adding a splash of the reserved pasta water to create a silky sauce that clings to the pasta.
Gently fold in the cooked nudi.
Serve immediately, topped with extra grated Parmesan cheese and a crack of black pepper.
Don't skip reserving the starchy pasta water. It's the key to creating a silky, emulsified sauce that clings perfectly to the pasta and nudi.
