From Cook’s Illustrated.
3 cups water
1 cup whole milk
1 tablespoon unsalted butter
1 cup steel-cut oats
¼ teaspoon table salt
Many supermarkets sell prepackaged steel-cut oats, but we found they were often stale and always expensive. A better option is to purchase them online from Bob’s Red Mill. To double the recipe, use a large skillet to toast the oats; increase the cooking time to 10 to 15 minutes once the salt has been added. If desired, pass maple syrup or brown sugar separately when serving, or try the Honeyed Fig Topping with Vanilla and Cinnamon.
Bring water and milk to simmer in large saucepan over medium heat. Meanwhile, heat butter in medium skillet over medium heat until just beginning to foam; add oats and toast, stirring constantly with wooden spoon, until golden and fragrant with butterscotch-like aroma, 1 ½ to 2 minutes.
Stir toasted oats into the simmering liquid, reduce heat to medium-low; simmer gently, until mixture thickens and resembles gravy, about 20 minutes. Add salt and stir lightly with spoon handle. Continue simmering, stirring occasionally with wooden spoon handle, until oats absorb almost all liquid and oatmeal is thick and creamy, with a pudding-like consistency, about 7 to 10 minutes. Off heat, let oatmeal stand uncovered 5 minutes. Serve immediately, with the following topping, if desired.