Milk makes mashed potatoes so rich and creamy, and it plays an important role in the structure as well. As Harold McGee, author of "On Food and Cooking," explains, when potatoes are cooked, the cells swell and separate, creating a dry and fluffy texture. Coating the pieces with liquid and fat brings the potatoes together and makes them smooth. Whether you're out of milk, on a dairy-free diet, or looking to try something new, there are many substitutes.
If dairy consumption is not a problem, try substituting all or part of the milk with cream. Half-and-half and light and heavy cream all work, though the higher the fat content, the stronger the flavor. Start with one-quarter of the amount of milk you'd normally use and add the substitute gradually until you reach the desired consistency and flavor.
Sour cream is a tangy and rich alternative. Add about 1/2 cup of sour cream per cup of milk in the original recipe; adjust to taste.
For another tangy substitute, try buttermilk at a 1:1 ratio.
Crème fraîche, added as 1 cup per 3 pounds of potatoes, makes super rich mashed potatoes.
Alternatively, to replace each cup of milk, add 1/4-cup instant dry nonfat milk plus 3/4 cup of the water the potatoes were cooked in.
If you prefer a non-dairy substitute, opt for a plant-based milk like soy, rice, oat, hemp, or almond milk. Substitute these at a 1:1 ratio. Consider adding an extra 1 to 2 tablespoons of vegan butter for richer potatoes that more closely mimic the fat in milk. Each plant-based milk brings its own flavor, and the potatoes will taste more earthy or nutty, depending on your choice. Coconut milk may also be substituted, but the flavor might be off-putting for some palates.
Substitute chicken or vegetable stock for hearty mashed potatoes. Choose a strong broth with full sodium for the most flavor, preferably homemade or a high-quality brand, and substitute it at a 1:1 ratio. Using broth cuts fat from the dish, making it a good choice if you're watching your caloric intake.
Vary the flavor and texture of mashed potatoes by mixing and matching milk substitutes. Use both broth and cream, or add a dollop of sour cream alongside the half-and-half. Add vegetable broth and soy milk in equal parts. Try substituting crème fraîche and light cream for an over-the-top decadent side dish. Enhance any of the substitutes by adding extra flavor, such as roasted garlic or freshly chopped sage.