In a large pot of boiling salted water, cook the spaghetti until just al dente or firm to the bite. Drain, reserving 1/2 cup of the pasta cooking water.
Meanwhile, in a small bowl, whisk the egg yolks and cream. In a large, deep skillet, heat the oil. Add the pancetta and cook over moderately high heat, stirring, until crisp, 4 minutes. Add the garlic and cook until golden, 1 minute.
Add the spaghetti to the skillet. Cook over low heat, tossing, until coated. Slowly add the reserved pasta cooking water and beaten egg yolks. Toss until coated with a creamy sauce, about 1 minute.
Add the 1 cup of Parmesan and the nutmeg; season with pepper. Transfer to bowls and serve, passing extra Parmesan.
