In the evening, put the rolled oats, milk kefir, raisins, and 1½cups of filtered water into a saucepan. Stir to combine and then cover the pot. Leave out at room temperature overnight.
In the morning, the oats and raisins will have soaked up most of the liquid from the night before. Add 1½ cups milk or nut mylk, another 1½ cups filtered water, salt, and cinnamon, and stir to combine.
Turn the stove on to medium heat, stirring frequently to prevent the porridge from burning on the bottom of the pot. When the porridge starts to simmer, turn the heat down to low and let the porridge continue to cook and thicken. Stir frequently.
Serve hot with cream, milk, or nut mylk. You can add chopped bananas or stewed fruit to give it a bit of sweetness, but the raisins may be enough for your liking. Enjoy!