Grease the bottom of the Instant Pot with coconut oil, butter, or a vegetable oil spray. Combine all the ingredients in the Instant Pot - from the steel cut oats to the chocolate chunks/chips and stir gently.
Close the Instant Pot lid and set the valve to sealing. Cook on the manual setting at high pressure for 15 minutes, with natural steam release. Once the pressure is released, carefully open the Instant Pot and stir the oatmeal. To serve, garnish with fresh cherries and more chocolate, if desired.
You can use any kind of milk - almond, soy, coconut, or cow's milk (skim, 1%, 2%, or whole). If using sweetened vegan milk such as vanilla almond milk, you might want to reduce the amount of agave nectar so the oatmeal doesn't turn out too sweet.
You can use more or less milk for this recipe - depending on how creamy and rich you like your oatmeal. Just make sure that the ratio of oats:liquid is 1:2. If using cow's milk, don't use more than 3 cups of milk (plus 1 cup of water), otherwise the milk might burn a little on the bottom of the Instant Pot.
If you plan on saving some oatmeal for the next day, stir in another cup of water or milk before putting the oatmeal into the refrigerator, otherwise the oatmeal will continue to gel up as it cools. Reheat in the microwave for 1-2 minutes, adding additional water or milk if necessary to get the desired thickness.