For the potatoes, cover them with cold water in a large pot and bring to a boil. Cook until fork-tender, then drain and return them to the hot pot. Move them around until most of the remaining water evaporates.

Transfer the potatoes to a large bowl and mash to your preferred chunky texture. Add the cream cheese, sour cream, scallions, parsley, salt, and pepper; mix and adjust seasoning to taste.

For the ham, drain the pineapple, reserving the juice. Place the pineapple chunks in the bottom of the Instant Pot and set the ham cut side down on top. Stir the tamari and ground mustard into the pineapple juice and pour it over the ham. Rub the brown sugar over the ham, letting any extra fall into the pot.

Seal the Instant Pot and pressure-cook on high for 10 minutes. Quick-release the pressure and remove the ham and pineapple chunks.

Set the pot to sauté. Mix the cornstarch with cold water, stir the slurry into the cooking liquid, and cook for a few minutes until thick and bubbly. Spoon the pineapple sauce over the ham and serve with the smashed potatoes.