Generously grease the inside of a 6-quart Instant Pot with cooking spray or softened butter.
Nonstick cooking spray
Add the steel-cut oats and water. Stir thoroughly, making sure no oats remain stuck to the bottom.
1 cup regular steel-cut oats, 3 cups water
Nestle the peeled sweet potato halves into the oat mixture with their cut sides facing up.
1 medium slender sweet potato
Spoon the brown sugar over the sweet potato halves. Sprinkle with cinnamon and nutmeg, then place 1 tablespoon butter on each half. Do not stir.
1/4 cup packed light brown sugar, 1 tsp ground cinnamon, 1/4 tsp ground nutmeg, 2 Tbsp salted butter
Secure the lid and set the valve to Sealing. Select Pressure Cook and cook on High Pressure for 15 minutes. The pot will need additional time to come to pressure before the countdown begins.
Allow a 10-minute natural release, then carefully release any remaining pressure according to your model’s instructions. If foam or liquid sputters from the valve, stop venting and allow additional natural release. Follow your model’s guidance for oatmeal, which may require a full natural release.
Once the float valve drops, carefully remove the lid. Check that the sweet potato yields easily to a fork. Mash it directly into the oatmeal, then add the vanilla and stir until combined.
1 tsp vanilla extract
Let stand for 5–10 minutes. Stir in milk or cream as needed for your preferred consistency. Spoon into bowls and serve with pecans, maple syrup or additional cinnamon, if desired.
milk or cream, chopped pecans, maple syrup, additional ground cinnamon