Add 2 Tbsp. butter to the Instant Pot and turn to saute. When the butter is melted add the pork loin and sear for 4 minutes. Turn the pork loin over and add the onions to the pot. Cook for 4 more minutes.

Add the chicken broth to the pot and cover. Cook on high pressure for 35 minutes. Allow the pressure to release naturally.

Remove the pork loin and set on a cutting board, allowing to rest.

Remove 2 c. liquid from the pot and reserve for the gravy. Add the box of the stuffing mix to the remaining liquid and onions and stir until all moistened. Cover with the lid and let sit for 5 minutes. Fluff the stuffing and add to a bowl and cover.

To the Instant Pot, add the remaining 2 Tbsp. butter and turn on to saute. (No need to clean out the pot first. The bits of remaining stuffing will just add a little flavor to the gravy) Melt the butter and add the flour. Whisk for 1 minute. Add the reserved 2 cups broth slowly, stirring to combine well. Cook for 1-2 minutes until thickened. Season with salt and pepper to taste.

After the pork loin has rested, cut and serve with the gravy and stuffing.