If desired, spray inside of Instant Pot with nonstick spray. Combine rice, 1 cup milk, water, and salt in Instant Pot. Close and lock the lid. Set for Pressure Cook (or Manual on High Pressure, depending on your model) for 5 minutes. It will take about 10 minutes to come to pressure. When timer goes off, let the pressure naturally release for 10 minutes (that is, do nothing for 10 minutes). After 10 minutes, release remaining pressure and remove lid.
Stir in brown sugar.
In a medium sized mixing bowl, whisk together half-and-half, 1 ½ cups milk, and eggs. Temper the egg mixture by gradually stirring in a half cup of the hot rice mixture. With Instant Pot on sauté function, gradually stir in the egg mixture.
Bring to a boil, stirring constantly and cooking for 2 to 3 minutes or until pudding begins to thicken. It will thicken much more as it cools.
Stir in vanilla, nutmeg, and raisins (optional). Immediately transfer pudding (be careful, it's very hot) to a bowl so that it doesn’t burn on the bottom.
Serve warm or cold.
Video
Notes
Nutrition information is calculated for a half cup serving, using half-and-half, and including raisins.
If your raisins are rather hard and dry, soak them in a cup of very hot water while the rice cooks. Drain well before adding to the pudding.
Leftover rice pudding can be stored in the refrigerator for up to three days. Enjoy it cold or reheat single portions gently in the microwave. If the pudding seems too dry or thick, stir in a splash of milk or cream.