Set Instant Pot to Saute mode and heat 1 tablespoon of butter or coconut oil. Add sweet potatoes, orange juice, salt, cinnamon, all spice and nutmeg. Mix together.
Spread 1/4 cup of brown sugar on top, do not mix. Close Instant Pot with pressure valve to sealing. Cook on Manual/Pressure cook(hi) for 5 minutes followed by quick release.
If serving from the Instant Pot, spread the remaining vegan butter or coconut oil over the potatoes. Sprinkle 2 tablespoon of brown sugar and arrange the pecans on top. Set Instant pot to saute(less) and cook for 5 mins or until the potatoes are heated through and the top becomes bubbly. Keep the sweet potatoes on 'keep warm' mode until ready to be served.
If you are serving in casserole, take the mashed sweet potatoes out in a casserole dish. Arrange pecans in a single layer on top. Sprinkle with 2 tablespoon brown sugar and drizzle remaining melted butter over the top. Bake for 15 minutes in a preheated oven at 375 degrees, or until browned and bubbly