The Reason The Milk In Your Scalloped Potatoes Is Curdling
As delicious as scalloped potatoes are, you may run into problems with this dish, especially where dairy is concerned. Scalloped potatoes at the very least call for milk, but milk can very easily curdle in the oven and render your cream sauce clumpy and unappetizing.
In many cases, curdling is the result of your dairy not containing enough fat to keep the protein molecules from binding to each other and creating clumps. As such, you should always use high-fat dairy –- be it whole milk, half-and-half, or even heavy cream -– and avoid cooking with skim milk, reduced-fat milk, and low-fat milk. High-fat dairy products contain enough fat to keep the proteins separate, and your sauce smooth.
Another common cause of curdling is your heat source being too hot. High oven temperatures can make the milk's components break apart, again leaving the proteins free to clump together. To prevent curdling, cook your scalloped potatoes at a lower temperature and across a longer period of time.
Other ingredients can keep scalloped potatoes from curdling
Interestingly enough, the star ingredient in scalloped potatoes can also reduce the risk of your cream sauce curdling. Potatoes' own starches help stabilize the fats and proteins present in the dairy, making curdling less likely. Therefore, the best spuds for scalloped potatoes are high-starch varieties like Russet, Yukon gold, or Idaho. To further lower the risk of curdling, you can add extra starch in the form of flour or cornstarch. Just a teaspoon or two is enough to stabilize the dairy, as well as to give you a lusciously thick sauce.
Of course, another highly important ingredient is cheese. Not every scalloped potato recipe calls for cheese, but when one does, you should abide by the same rules as those for milk. Use only high-fat cheeses –- cheddar, fontina, gouda, or mozzarella -– in order to keep the dairy proteins separated. After all, you've already put so much work into choosing the right milk and potatoes; it would be heartbreaking to ruin your recipe with the wrong cheese.
Upgrade your scalloped potatoes with fun flavors
Now that you've got all the basics for preventing scalloped potatoes from curdling, you can move on to spicing your recipe up a bit. Some more common extras include caramelized onions, fresh herbs, and ham, but the possibilities are truly endless. Add in sliced veggies for a scalloped potatoes and ratatouille crossover. Give your scalloped potatoes a little kick with chiles or salsa. Top the dish off with potato chips for salt and crunch. Anything goes.
Likewise, you can easily upgrade this potato dish with a can of soup. Your best bet is some kind of creamy soup, like celery or mushroom, so it will mix more seamlessly with the rest of your cream sauce and help thicken it. Whatever soup you decide to use, add it to the scalloped potatoes before baking, and be sure to add enough to cover the potatoes. When your dish is done, the potatoes will have soaked in all the flavors of the soup, becoming deliciously tender.