In a large pot of boiling salted water, cook pasta according to package instructions; reserve 1/2 cup water and drain well.
In a small bowl, whisk together eggs and Parmesan; set aside.
Heat a large cast iron skillet over medium high heat. Add bacon and cook until brown and crispy, about 6-8 minutes; reserve excess fat.
Stir in garlic until fragrant, about 1 minute. Reduce heat to low.
Working quickly, stir in pasta and egg mixture, and gently toss to combine; season with salt and pepper, to taste. Add reserved pasta water, one tablespoon at a time, until desired consistency is reached.
Serve immediately, garnished with parsley, if desired.
Notes
Reserve the pasta water. Thanks to the starch in the pasta water, this will help the sauce stick to the pasta as well as thicken the sauce for extra creaminess.
Make it authentic. Bacon is readily available but pancetta or guanciale can also be used for a more authentic-style carbonara. Diced uncured pancetta from Trader Joe's is a great swap for the bacon here.
Freshly grated cheese goes a long way. While pre-grated cheese will save a few minutes in the kitchen, freshly grated Parmigiano Reggiano or domestic Parmesan is ideal, creating that smooth, silky, glossy consistency.
Use room temperature eggs. Using room temperature eggs will ensure a smooth, well-emulsified silky consistency (cold eggs can seize when added to hot pasta). To quickly bring eggs to room temperature, place the eggs in a bowl of warm water for about 10 minutes. Do not leave the eggs at room temperature for over 2 hours.
Make it richer. For an even richer, creamier consistency, use egg yolks only.
Add the egg mixture into the center. Add the egg mixture to the middle of the skillet over the pasta, working carefully to avoid the edges. Toss immediately, quickly and consistently to avoid overcooking and scrambling.
Lower the heat. Allow the residual heat from the pasta to cook the eggs gently to yield that velvety, silky sauce. Remove the pan from heat if needed.
Halve the recipe. If cooking for 2, say for date night or a romantic night in, this recipe halves very well. Utilize the same cooking time with a smaller cast iron skillet.