Step 1

In a large heatproof mixing bowl, whisk together whole eggs and yolk, Pecorino Romano, Parmigiano-Reggiano, and black pepper. Set aside.

Step 2

In a large skillet, melt butter over medium heat. Add garlic and cook, stirring and turning cloves occasionally, until garlic begins to soften and turn pale golden, about 3 minutes. Turn off heat.

Step 3

Meanwhile, in a pot of salted boiling water, cook pasta until al dente. Right before pasta finishes cooking, remove garlic cloves from skillet and discard. Using a spider skimmer, transfer pasta to skillet; be sure not to drain boiling pasta cooking water, and reduce heat to a simmer.

Step 4

Stir and toss pasta rapidly in skillet to evenly coat with butter, then transfer to bowl with egg-cheese mixture, using a rubber spatula to scrape all of the butter into the bowl. Add 3/4 cup (180ml) of reserved pasta cooking water to bowl, and stir to thoroughly combine.

Step 5

Set bowl over pot of simmering pasta cooking water (making sure bottom of bowl does not touch water) and cook, stirring and scraping down sides of bowl constantly with a rubber spatula, until sauce thickens to a creamy, silky consistency and leaves trails as you stir, about 1 minute, adding more pasta cooking water in 1 tablespoon (15ml) increments as needed to adjust consistency of the sauce.

Step 6

Remove bowl from heat, add parsley (if using), and stir to combine. Season with salt to taste. Divide between warmed serving bowls, and serve.