Crack the eggs into a bowl and whisk them. Add the grated Pecorino Romano and Parmesan cheeses to the eggs. Mix until well combined. Set aside.

Dice the pancetta or guanciale and mince the garlic.

Turn on your Instant Pot and select the "Sauté" function. Add the diced pancetta or guanciale and cook until it becomes crispy and releases its fat, about 4-5 minutes.

Remove the cooked pancetta/guanciale using a slotted spoon and set it aside, leaving the fat in the Instant Pot.

Add the minced garlic to the Instant Pot and sauté for about 30 seconds until fragrant.

Break the spaghetti in half and add it to the Instant Pot. Stir well to coat the pasta with the fat.

Add 3 cups of water (or enough to fully cover the pasta), a pinch of salt, and a generous amount of freshly ground black pepper.

Cancel the "Sauté" function, close the Instant Pot lid, and set the vent to "Sealing." Select the "Pressure Cook" or "Manual" function and set it to cook on high pressure for half of the pasta's package cooking time minus 1-2 minutes (usually around 3-4 minutes).

Once the cooking cycle is complete, perform a quick pressure release. Carefully open the lid once the pressure has fully released.

The pasta should be al dente. If it's slightly undercooked, that's fine, as it will continue to cook in the next step.

Immediately add the whisked egg and cheese mixture to the cooked pasta. Stir vigorously to combine, allowing the residual heat to cook the eggs and create a creamy sauce. If needed, you can turn on the "Sauté" function on low to help thicken the sauce, but be sure to stir continuously to avoid scrambling the eggs.

Add the crispy pancetta or guanciale back into the pot and stir it in.

Once the sauce is creamy and the pasta is well-coated, turn off the Instant Pot. Taste and adjust the seasoning with salt and more black pepper if desired.

Serve the Pasta Carbonara immediately, garnished with chopped fresh parsley and additional grated cheese, if desired.