Bring a large pot of water to a rolling boil. Add 1 tablespoon of salt (it should taste like seawater).

While water heats, place guanciale strips in a cold large skillet. Set over medium heat and cook, stirring occasionally, until fat renders and the meat is golden and crispy, about 8–10 minutes. Remove skillet from heat but keep the guanciale and its rendered fat in the pan.

In a medium bowl, whisk together the whole egg, 3 egg yolks, 1 cup of grated Pecorino Romano, and 2 teaspoons of black pepper until smooth and well combined.

Add spaghetti to the boiling salted water and cook until al dente according to package directions (usually about 10 minutes). Just before draining, reserve about 1.5 cups of the starchy pasta water.

Drain the spaghetti and immediately transfer it to the skillet with the guanciale (the skillet should be off the heat). Toss well to coat the pasta in the rendered fat. Let it cool slightly for 1 minute so the eggs won't scramble.

Pour the egg and cheese mixture over the pasta, tossing vigorously with tongs or a fork. Gradually add small splashes of the reserved pasta water (about ½ cup total, a little at a time) while tossing. Continue cooking and tossing until the sauce thickens and reaches an internal temperature of 160°F (71°C) for food safety – use a thermometer. If it hasn't reached temperature, return the skillet to very low heat for 30 seconds while tossing constantly, then remove from heat. The sauce should be creamy, silky, and cling to each strand.

Divide the carbonara among warm plates or bowls. Top with extra grated Pecorino Romano and a generous crack of black pepper. Eat right away while creamy and hot.