Pour 1 cup of water in the Instant Pot and insert a steamer basket. Place potatoes in basket, then secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOK function*. Use the +/- keys and program the Instant Pot for 20 minutes.
Meanwhile, in a small bowl, combine the Topping Mixture ingredients and mix until well-combined. Set aside.
When the cook time is up, quick-release the remaining pressure. Carefully remove and peel the potatoes.
In a large bowl, mash together the potatoes and orange juice. Add remaining Potato Mixture ingredients and mix well.
Coat the inside of a 1.5 qt casserole with nonstick spray and spread potato mixture evenly in the dish.
Sprinkle prepared topping evenly across the top of the potatoes and cover loosely with foil--do not seal.
Ensure there is still one cup of water in the Instant Pot and add the steam rack. Use a foil sling to carefully lower the casserole onto the steam rack and secure the lid, making sure the vent is closed.
Using the display panel select the MANUAL or PRESSURE COOK function*. Use the +/- keys and program the Instant Pot for 15 minutes.
When the time is up, quick-release the remaining pressure.
(Optional) Set the casserole under the broiler for 3-5 minutes to crisp up the topping.