To make the oats, bring the water to a boil in a deep pot. Add oats and cook until they begin to thicken. Reduce to a simmer, and continue cooking, uncovered, until grains are slightly tender and water has mostly absorbed, about 15 to 20 minutes. Turn off heat, cover pot and let sit for 5 minutes before serving.
Make-ahead: Steel cut oats reheat very well, so I like to make extra this way we can enjoy them on busy weekday mornings. Store leftovers in a covered container. Spoon our individual portions into a bowl, adding a tablespoon or two of milk or water, then cover and microwave until heated through, about 1 minute does the job in my 1000 watt microwave.
To serve, add ½ cup of cooked oats to a deep bowl. Scatter sugar or honey and raisins on top. Add ricotta cheese and sprinkle pistachios on top. Serve immediately—I like to stir it all up so I get a bit of everything in each spoonful!