This is a true giant in classic Italian cookery usually done on the stove but I can promise you it works beautifully in the Instant Pot too!
Start by cooking the pancetta (or guanciale) on Sauté mode until the fat has rendered out - remove the cooked pancetta to a plate and discard most of the fat. I leave about 1 tsp worth behind. Cancel Sauté mode.
Place the pasta nests in the inner pot and cover with at least 1.5 inches of cold water. Check how long the packet says it takes for the pasta to cook and halve it (see notes). Place the lid on, program the requisite number of minutes on Manual High.
Meanwhile, whisk the eggs, cheese, nutmeg and black pepper together in a jug or bowl. Feel free to add more cheese - 1/4 cup if I'm being virtuous, a half cup if I need comfort food stat! ;)
When the timer goes off for the pasta, wait 30 seconds for the pasta to settle and then release the pressure (do a QPR) - again see notes below. Strain the pasta over a bowl so you keep the starchy cooking water.
Return the Inner Pot to the base and put it back on Sauté and adjust to Low. Quickly add back the cooked pancetta, the drained pasta and the egg and cheese mixture. Stir gently but thoroughly until the pasta is covered in the sauce which will cook in the gentle heat. Use the reserved pasta water to loosen the texture as desired and serve in deep bowls with extra black pepper and cheese on top. Devour immediately!