Cook the pasta according to the package directions. Drain and set aside.
In a large skillet, heat the olive oil over medium heat and sauté the chicken pieces until browned and cooked through. Remove from the skillet and set aside.
In the same skillet, add butter and sauté the onion until it is soft and translucent. Add the garlic and cook for another minute.
Add the heavy cream to the skillet, bring to a simmer, and stir in the Parmesan cheese, nutmeg, salt, and pepper until the sauce is smooth and thickened.
Return the cooked chicken to the skillet and stir to coat with the sauce.
Add the cooked pasta shells to the skillet and gently toss to combine all ingredients with the sauce.
Garnish with fresh parsley before serving hot.
Notes
Use fresh Parmesan for a creamier sauce and experiment with additional herbs like basil for extra flavor.