Add butter to the Instant Pot. Using the display panel select the SAUTE function.

When butter is melted, add garlic and cook for 1 minute or until lightly browned.

Add broth, lemon zest and 1 tbsp of lemon juice to the pot and deglaze by using a wooden spoon to scrape any brown bits from the bottom of the pot.

Break noodles in half and fan across the bottom of the pot, making sure all noodles are submerged.

Turn the pot off by selecting CANCEL, then secure the lid, making sure the vent is closed.

Using the display panel select the MANUAL or PRESSURE COOK function (*The MANUAL and PRESSURE COOK buttons are interchangeable). Use the +/- keys and program the Instant Pot for 3 minutes.

When the time is up, let the pressure naturally release for 10 minutes, then quick-release the remaining pressure.

Stir, breaking up any pasta clumps and allow to cool slightly.

Add parmesan cheese, half-and-half and remaining 2 tbsp of lemon juice. Add salt and white pepper to taste.

In a small bowl, mix together cornstarch and cold water. Stir into the pot until thickened, using SAUTE mode, as needed.

Serve warm topped with grilled chicken (optional), finely chopped parsley and additional parmesan.