What Makes Costco's Scalloped Potatoes So Delicious?

A good main dish deserves a good side. At Costco, people can find a plethora of possible sides, including products sold under the chain's famed Kirkland brand, such as mixed salads or mac and cheese. But the store brand isn't the be-all and end-all. One of the most comforting options you can find at Costco isn't a Kirkland brand item but the Main St Bistro Scalloped Potatoes, made by Reser's. Everyday Fun Finds described the dish as "perfectly creamy and not too cheesy," adding that "scalloped potatoes are the perfect comfort food, and I was surprised by how delicious these tasted."

Main St Bistro's Scalloped Potatoes are made from thinly sliced spuds that have been baked in a bath of dairy and covered in cheese. They are stocked in the refrigerated section near Costco Deli — as well as being available at Sam's Club and other retailers. Clocking in at a hefty 40 ounces, enough for 8 people, this cheesy, creamy casserole of potatoes can cost less than a dollar per portion at $7.79. Though, prices may vary by location. The package states that the scalloped potatoes can be ready in nine minutes, using a microwave oven, but for best results, they really should be baked. Though the scalloped potatoes have already been cooked in the oven, so just need reheating, an oven will bring them up to temperature more evenly and also create a better 'au gratin' finish to the cheddar cheese layer on top. But what's the secret of their success?

Making scalloped potatoes is a labor-intensive process. Peeling, slicing, and baking the potatoes takes several hours. To get uniform thickness, need a specialist slicer like a mandoline. To get a tangy, yet melting blend of cheeses and cream, you'll need to buy many different dairy products. Instead of all that fuss, Main St Bistro's scalloped potatoes are ready in 10-20 minutes, and at a price point well below what you'd spend to get together all of those ingredients on your own.

Scalloped potatoes live and die by the quality of the potato that's used. Per a Sam's Club product description, Reser's uses premium russets. That same variety forms the backbone of Reser's potato salad, the dish on which the brand was founded. Russets are perfect for scalloping. Their high starch level means that they break down quicker than a waxy variety. The starchiness also helps to thicken the sauce and give it even more silkiness.

This traybake doesn't skimp on dairy — the cheese topping opens it up to debate about whether it's really 'scalloped potatoes' or more 'potatoes au gratin'. But, the distinction between these similar dishes matters less than the blend of cheddar and parmesan packing a serious flavor punch. Using whole milk and butter for the sauce holds nothing back on the fats front, meaning the liquid is decadent before the starches even begin to thicken them further, and sour cream adds a welcome tang while doing nothing to reduce the richness.

Chefs are always saying it's impossible to make superior products with inferior ingredients. Home cooks know that you can cobble together the best ingredients in the world, and screwing them up is just as easy as it is with the cheap stuff. Raw materials are very important, but technique matters too. We've spotted a few tweaks in the recipe that ensure Costco scalloped potatoes don't fall foul of the pitfalls that face cheesy potato casseroles everywhere.

Firstly, there's added starch. The platonic ideal of potatoes au gratin — i.e. the most refined, French version — relies solely on the starches already present in the potato to set the dish. The way starches thicken up the cooking liquid plays a large part in creating the extra creamy texture we love. So, there's a smidgen of cornstarch in the Costco scalloped potato sauce — and they're better for it.

Secondly, they're pre-cooked. This might sound obvious, but the two most common ways that scalloped potatoes fall short are caused by an oven that's too hot, or a cooking time that's too short. These will split the sauce or undercook the spuds, respectively, and buying a casserole that's 95% finished practically eliminates these considerations.

Finally, they're the kind of versatile, ready-to-eat side that allows cooks with a bit of ambition to hit home-run meals. Rarely will Costco scalloped potatoes be the star of the show, but they can absolutely set the stage for you to be the star.