In a medium-sized pot over high heat, add the milk, water, and salt. Combine, stirring frequently as the liquid comes to a gentle simmer.
Lower the heat to medium and add both kinds of oats
Stirring frequently (lowering the heat as needed to maintain a good simmer), cook the oats.
After about 20 minutes, the rolled oats will have turned a bit mushy, while the steel-cut oats will be just tender and will pop when you bit into them
Taste for seasoning (they should be on the salty side)
Add sugar or syrup.
Spoon the porridge into warm bowls and let it sit for a minute or two
(Note: Included below is the topping suggested by April Bloomfield. For other topping ideas, see above)
Then carefully pour a little cold milk around the edges of each bowl, so it pools all the way around.
Sprinkle a five-fingered pinch of sugar or drizzle the syrup in the center of each and let it melt, then serve right away.