Put fettuccini into large pot of boiling water.
Melt butter in a large skillet or saucepan. Once it's melted, add the half-and-half and stir. Let it warm up, then turn down the head to medium-low.
Stir int he parmesan cheese. Keep stirring! Let it heat slowly, stirring almost constantly until it's melted and smooth. Stir in the nutmeg, salt & pepper. Remove from heat and stir in the proscuitto.
The fettucin will be done about the same time as the sauce. Drain it & toss it with the sauce.