Boil the Eggs: Place your eggs in a pot and cover them with cold water. Set the pot on high heat. When the water starts to boil, turn off the heat, cover the pot, and let the eggs sit for 10 minutes. Then, move the eggs into a bowl of ice water to cool.
Cook the Guanciale: While the eggs cool, cook the guanciale in a pan over medium heat until it turns crispy and brown. Remove the crispy pieces and save 1 tablespoon of the fat for later.
Separate the Yolks and Whites: Peel the eggs, then carefully slice them in half lengthwise. Remove the yolks and place them in a food processor (or a bowl if you’re mashing by hand).
Make the Filling: Add mayonnaise, pecorino cheese, the reserved guanciale fat, salt, black pepper, and water to the yolks. Blend (or mash) until the mixture is creamy and smooth.
Pipe the Filling: Use a piping bag (or a zip-top bag with a corner cut) to fill the egg whites with the yolk mixture.
Garnish: Top each deviled egg with crispy guanciale, a sprinkle of grated pecorino cheese, and a little black pepper.