To prepare the Fettuccine alla Papalina with peas, begin by heating the butter (or olive oil) in a non-stick skillet. Add the finely chopped onion and gently cook until translucent. Add the peas, cover with a lid, and simmer over low heat for 20–25 minutes.
Towards the end of the cooking time, add the diced ham, season with salt, and keep warm. Meanwhile, in a bowl large enough to eventually hold the pasta, lightly beat the eggs with two tablespoons of grated Pecorino and freshly ground black pepper.
Cook the fettuccine in salted boiling water until al dente. Drain, reserving a cup of the starchy cooking water, and immediately toss the pasta with the beaten eggs so they gently cook from the residual heat, coating the strands like a velvety veil.
Add the peas and ham, then top with an extra sprinkle of grated Pecorino. Toss thoroughly and quickly, yet gently, to avoid breaking the fettuccine. If the mixture appears too dry, stir in a splash of the reserved pasta cooking water.
Finish with freshly ground black pepper, divide into individual serving bowls, and serve immediately.
