Add potatoes, garlic, and kosher salt to the Instant Pot.
Pour in the chicken stock just until it covers the potatoes. This may be more or less than the 5 cups called for in the recipe.
Attach the lid and ensure the valve is in the “sealing” position.
Set the Instant Pot to the Pressure Cook Manual, high heat, for 25 minutes.
When finished, manually release the pressure by switching the valve to "vent." Be careful hot steam will come out of the valve. When fully released remove the lid.
Save 1/4 cup of the hot stock from the Instant Pot and drain off the rest of the stock by straining it in a colander.
Add the potatoes back to the Instant Pot and add in the sour cream, heavy cream, and butter.
Mash until smooth. Use the reserved stock to help thin out the mashed potatoes to reach your desired texture.
Taste, season with kosher salt or black pepper, stir in the Italian seasoning and stir in the chives.
Notes
Use water in place in place of chicken stock.
Use vegetable stock in place of chicken stock.
Add more or less garlic depending on the flavor you're craving.
The potatoes do not have to be finely diced or chunked so I like to use smaller potatoes sand either halve or quarter them depending on size.