Bring a large pot of salted water to a boil and cook the pasta one minute less than the package instructions. After you drain the pasta, add a small splash of olive oil and toss it gently to keep the pasta from sticking. In a mortar and pestle (or grinder), add 2 teaspoons of black peppercorns and grind them until finely cracked. Set aside until ready to use.
In a medium saucepan, add the ground Italian sausage and cook over medium-high heat until browned. If the sausage is very oily, use a paper towel to remove any excess oil so the sauce stays balanced. Then turn off the heat and set aside until ready to use.
In a separate large deep saucepan, set to low-medium heat, add the butter. Once melted, add the ground pepper and the minced garlic. Cook on low, stirring often, until fragrant, letting the pepper infuse into the butter.
Pour in the heavy cream and nutmeg. Using a whisk, whisk until the nutmeg is combined, then bring to a low simmer for 3 to 4 minutes, allowing it to reduce slightly.
While the cream simmers, freshly grate your parmesan cheese - this ensures a silky smooth sauce without any grittiness. Once the cream is slightly reduced, add the parmesan cheese a quarter cup at a time, whisking well after each addition, waiting until fully melted before adding more. Allow the sauce to simmer until thickened.
Add the cooked Italian sausage to the cream sauce, along with the drained pasta. Increase the heat to medium and stir everything together, allowing the flavors to meld. Taste and adjust seasonings if needed - no added salt is usually required.
Turn off the heat, transfer the pasta to a large serving bowl, and garnish with toasted walnuts, lemon zest a more parmesan cheese.
Serve right away.