How to Make It
Whisk egg yolks, egg, Parmesan, and pecorino Romano together in a small bowl. Reserve at room temperature.
Cook pancetta in a skillet over medium, stirring occasionally, until crisp, about 6 minutes. Using a slotted spoon, transfer to a plate lined with paper towels. Reserve drippings.
Cook pasta in a pot to al dente according to package instruction. Reserve 1 cup of the cooking water. Place a strainer in a large metal bowl. Pour pasta and remaining cooking water into strainer, letting strainer with pasta stand in water, and allowing the metal bowl to heat, about 1 minute. Remove strainer with pasta, and pour cooking water back into pot. Transfer pasta from strainer to the warm metal bowl.
Place metal bowl of pasta on top of pot to keep warm. Stir in egg and cheese mixture, and stir constantly, adding reserved cooking water, as needed, to create a creamy sauce, about 2 minutes. Drizzle in reserved drippings, and stir to combine. Divide pasta between 2 bowls. Top with black pepper and pancetta; garnish with cheese.