Bring a pot of salted water to a boil and cook the pasta according to package directions; drain and set aside.
Heat a medium skillet over medium heat, then add the butter and heavy cream, stirring until the butter melts and the mixture is combined.
Stir in the white pepper and nutmeg, then continue to heat until the sauce just begins to bubble gently.
Add the grated cheese and stir constantly until the cheese melts into the sauce and it is smooth.
Remove the skillet briefly from the heat, add the egg yolk, and whisk or stir vigorously to combine quickly and temper the yolk without scrambling.
Toss the cooked pasta with the sauce until evenly coated, then serve immediately.