Peel and cube the sweet potatoes into small chunks. Place them in a steaming basket. Pour water in the Instant Pot. Close the lid, seal the steam release valve, and cook on high pressure for 10 minutes.
Once the cooking time is complete, quick release the pressure. Carefully remove the steaming basket. Drain the water, then place the cooked sweet potatoes back into the pot (or in a bowl).
Add butter and milk. Mash with potato masher until you have a smooth texture. Fold in the vanilla, cinnamon and sea salt. Serve with additional butter and/or chopped pecans on top.