What can I substitute for milk in boxed au gratin potatoes?

If you want to make boxed au gratin potatoes but don’t have milk on hand, there are a few good substitutes you can use instead. The most common milk substitutes for cooking and baking are non-dairy milks, water, and chicken or vegetable broth. Each substitution will provide a slightly different flavor and texture, so consider which option will work best for your needs.

Quick Answer

The best substitutes for milk in boxed au gratin potatoes are:

  • Non-dairy milk: Soy, almond, oat, or coconut milk
  • Water
  • Chicken or vegetable broth
  • Cream or half-and-half

Non-dairy milks like soy or almond milk are the closest 1:1 substitute, while water or broth will result in a thinner consistency. Cream or half-and-half will make the potatoes richer and more decadent.

Non-Dairy Milk

Replacing regular milk with non-dairy milk is the most direct substitution. Non-dairy milks like soy, almond, oat, and coconut milk have a similar creamy texture and neutral flavor like dairy milk. When using non-dairy milk in savory dishes like au gratin potatoes, opt for unsweetened varieties to avoid adding extra sweetness.

Soy milk is the most popular non-dairy alternative and is made from soybeans, so it has a similar protein content to cow’s milk. Almond milk has a watery consistency but still provides creaminess, while oat milk offers a mild oat flavor. Coconut milk is extra rich and creamy. Any of these will mimic the texture and flavor of regular milk in your potatoes.

The overall taste and consistency will be very similar to using regular milk. Non-dairy milk may result in slightly softer and less browned potatoes on top if baked. Make sure to stir the dish well after adding the non-dairy milk so it distributes evenly and thickens the sauce.


  • Very similar texture and neutral flavor
  • Easy 1:1 milk replacement
  • No significant changes to the dish


  • May be slightly less browned/caramelized on top
  • Some non-dairy milks are thinner and won’t thicken as well
  • Could alter flavor slightly depending on type used


Plain water is another suitable milk substitute for boxed au gratin potatoes. The potato flakes and cheese powder in the boxed mix contain starch and protein which helps thicken and emulsify the water into a creamy sauce.

Using water instead of milk reduces the overall richness, but the sauce will still thicken up adequately. The cheese flavor also comes through prominently. The resulting au gratin potatoes will be lighter than the original recipe.

Use hot water right from a recently boiled kettle for best results. Cold water straight from the tap won’t thicken as well. Stir the potatoes vigorously after adding the water to fully hydrate the potato flakes.


  • Readily available
  • Still thickens from the starches
  • Lets cheese flavor shine


  • Thinner, less creamy texture
  • Watery sauce
  • Missing richness from fat in milk


Chicken, vegetable, or beef broth can also substitute for milk in boxed au gratin potatoes. Using broth instead of milk gives the dish more savory umami flavor.

Low sodium or no sodium added broth works best to control the overall saltiness. Broth contributes saltiness on its own, so you likely won’t need to add any extra salt. The starch and emulsifiers in the potato mix will still help thicken the broth into a sauce.

Veggie or chicken broth provide an underlying background flavor. Beef broth makes the dish more meaty. Stir the broth well when adding it to fully incorporate. The potatoes may take on a light broth flavor but the cheese still comes through.


  • Adds savory flavor
  • No major change in texture
  • Potatoes soak up meaty flavors well


  • Alters the original flavor
  • Could make it saltier
  • Runnier consistency if not thickened properly

Cream or Half-and-Half

Heavy cream or half-and-half are luxurious substitutes for milk that make extra rich and decadent au gratin potatoes. They add a creamy, indulgent texture with some tang.

The higher fat content in heavy cream or half-and-half gives the sauce a silkier, thicker consistency. This makes the potatoes more moist with a delightful creamy mouthfeel. They brown exceptionally well during baking too.

Take care not to add too much cream – a 1:1 ratio with the milk amount can make it overly greasy. Start with less and add more as needed. The sauce may break if overheated, so gently warm the cream before adding.


  • Very creamy, decadent texture
  • Bakes up nicely browned and crusty
  • Adds rich flavor


  • High fat content makes it heavy
  • Can make the sauce too thin if added excessively
  • More expensive option

What About Sour Cream or Yogurt?

Dairy products like sour cream and yogurt are not the best substitutes for milk in boxed au gratin potatoes. Although they seem creamy, their thickness and tangy flavor can throw off the intended texture and taste.

Sour cream is very thick, so it needs to be thinned out with water or broth to make a pourable sauce. It tastes pleasant but makes the potatoes overly tangy. Plain yogurt is thin but adds sourness. Greek yogurt is too dense. Overall, sour cream or yogurt change the flavor profile too much.

If you want to use them, blend sour cream or yogurt with broth or water first. Start with just a few tablespoons blended into 1 cup liquid. The potatoes will still have a hint of tang but less than using alone. The sauce may also curdle from the acidity, so stir gently when adding.

Tips for Using Milk Substitutes

When using any milk substitute in boxed au gratin potatoes, keep these tips in mind:

  • Check the consistency and adjust as needed. Non-dairy milk or broth may appear too thin at first, but will thicken up after simmering with the potato mix. Add a bit of flour or cornstarch if it remains watery.
  • Increase cooking time if needed. Some subsitutions like water result in a runnier sauce, so you may need to bake the potatoes longer to evaporate excess moisture.
  • Stir gently to avoid clumping. Aggressively whisking or stirring can make the potatoes gluey or clumpy. Fold lightly to incorporate.
  • Add cheese as needed. If the sauce seems underseasoned, extra shredded cheese sprinkled on top enhances flavor.
  • Use hot liquid for full thickening power. Cold ingredients thin out the sauce rather than thicken it.

Sample Substitution Ratios

Refer to this simple chart for easy substitution ratios when replacing milk in boxed au gratin potatoes:

Milk Substitution Ratio
1 cup milk Non-dairy milk 1 cup
1 cup milk Water 1 cup
1 cup milk Broth 1 cup
1 cup milk Heavy cream 3/4 cup
1 cup milk Half-and-half 1 cup

Recipe Example: Au Gratin Potatoes with Almond Milk

Here is a recipe for au gratin potatoes using almond milk instead of regular milk:


  • 1 box (5.8 oz) au gratin potato mix
  • 1 cup unsweetened almond milk
  • 1 1⁄2 cups water
  • 1 tbsp butter
  • 1 cup shredded cheddar cheese


  1. Preheat oven to 400°F. Grease an 8-inch square baking dish with butter.
  2. Bring the almond milk and water to a simmer in a saucepan. Add the potato mix and butter. Whisk for 1 minute until thickened.
  3. Pour the potato mixture into the prepared baking dish. Top evenly with the shredded cheese.
  4. Bake for 25 minutes until hot and bubbly. Brown under the broiler for 3-5 minutes if desired.
  5. Let rest 5 minutes before serving.

The Best Milk Substitute for Box Au Gratin Potatoes

When considering taste, texture, and ease of use, the best milk substitute for box au gratin potatoes is unsweetened non-dairy milk. Non-dairy milks like almond and soy maintain the creaminess of dairy milk with a neutral flavor that doesn’t detract from the cheese sauce.

Broths make a decent substitute for adding more savory flavor, while water or cream provide options for lighter or richer sauces. Avoid thick, tangy dairy products like sour cream or yogurt which alter the flavor too much. With so many milk alternatives available, you shouldn’t have to skip au gratin potatoes if you run out of regular milk!

Frequently Asked Questions

Can I use potato water instead of milk?

Using the starchy potato water leftover from boiling potatoes is not recommended as a substitute for milk. It can lend an unpleasant flavor and may not provide enough creaminess or fat for the sauce.

Is powdered milk a good substitute?

Reconstituted powdered milk can work in a pinch but isn’t ideal. It won’t provide the same richness and texture as fresh milk. Mix powdered milk as directed and use it as a 1:1 replacement.

Can I make it completely dairy free?

Yes, you can make au gratin potatoes dairy-free by using water or broth instead of milk and omitting real cheese. Rely on the potato flakes and cheese powder in the boxed mix for flavor. Top with non-dairy cheese like Daiya for extra cheesiness.

Should I use skim, 2%, or whole milk?

Whole milk provides the most creaminess, but 2% or 1% milk work well too. Skim milk tends to result in a thinner, less rich sauce. For best texture and flavor, opt for 2% or whole milk.

Is soy milk a good option?

Yes, soy milk can be substituted 1:1 for cow’s milk. Its relative thickness, protein content, and neutral flavor make it a great non-dairy option for creamy au gratin potatoes.


There are a variety of easy ingredient swaps when you don’t have regular milk for boxed au gratin potatoes. Non-dairy milks offer the most similarity in taste and texture. Broth provides added savory flavor, while water or cream allow you to make the dish lighter or richer. With so many milk substitutes to choose from, you don’t have to let a missing ingredient prevent you from enjoying au gratin potatoes.

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