Add the water, milk, salt, oats, vanilla bean, cinnamon stick and raisins to the pressure cooker.
Bring the cooker to high pressure over high heat, then lower the heat and cook under pressure for 3 minutes. The cooking time starts once the pressure is up. Then, remove it from the heat and allow the pressure to come down naturally. During this time, the oats will continue to cook.
Then, carefully remove the lid and check to see if the oats are cooked enough. Mine were not at this point. If not, remove the pot from the heat, lock on the lid, and let them sit for another 10 minutes. They will continue cooking during this time.
Remove the lid. Then remove the vanilla bean and cinnamon stick and set aside. Stir in the cinnamon, walnuts, and agave syrup to taste.