Place 5 large sweet potatoes in pressure cooker on top of trivet and add water. Lock lid and set manual timer for 20 minutes at high pressure. Once cook time is complete, allow pressure to release naturally (about 15 minutes).
Meanwhile, while potatoes are cooking – in a small sauce pan over medium heat, add butter, brown sugar, vanilla, salt, nutmeg, and lemon juice. Heat and mix until fully melted. Then add evaporated milk and bring to a simmer.
Remove skin from potatoes and also trim any dark spots. Transfer potatoes to large mixing bowl.
Pour milk mixture into mixing bowl and thoroughly mash and mix potatoes