Bring a large pot of generously salted water to a boil. Cook the spaghetti until al dente, about 1 minute less than the package says. Reserve at least 2 cups of starchy pasta water before draining.

While the pasta cooks, add the guanciale to a cold large skillet, then set over medium heat. Cook, stirring occasionally, until the fat renders and the meat is crisp and golden, about 8–10 minutes, and the guanciale reaches an internal temperature of 145°F (63°C). Turn off the heat but leave the skillet on the burner.

In a large bowl, whisk together the egg yolks, whole eggs, grated Pecorino, and black pepper until smooth and pale.

Working quickly, transfer the drained hot pasta directly into the skillet with the guanciale (off the heat). Toss well to coat. Pour the egg mixture over the pasta and toss vigorously, adding a splash of reserved pasta water at a time until a creamy, silky sauce forms—about 1/4 cup in total. For food safety, the egg mixture should reach 160°F (71°C); use an instant-read thermometer to check. If the temperature is too low, continue tossing and add more hot pasta water as needed. The pasta should be glossy, not soupy.

Divide immediately among warmed bowls. Crown each with a blizzard of freshly grated Pecorino and more cracked black pepper. Serve right away.