Recipe Review

I Tried Serious Eats’ Brown Butter Sweet Potato Casserole and the Results Surprised Me

published Nov 15, 2022
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sweet potato casserole recipe by Serious Eats in baking dish on marble
Credit: Photo: Andrew Bui; Food Styling: Jessie YuChen

Serious Eats is one of my go-to sites when I’m looking for recipes for classic dishes. It’s home to my favorite green bean casserole, so when testing sweet potato casseroles I figured I’d take a peek over there to see what they had to offer.

Like most Serious Eats recipes, each step in the process is written with considerable thought. The natural sweetness of the sweet potatoes is maximized through slow-roasting, then tempered by several savory mix-ins like browned butter and fresh herbs. As someone who often finds sweet potato dishes too sweet, I was intrigued.

Get the recipe: Serious Eats’s Sweet Potato Casserole With Marshmallows

Credit: Photo: Andrew Bui; Food Styling: Jessie YuChen

How to Make Serious Eats’ Sweet Potato Casserole with Marshmallows

This recipe starts by slow-roasting whole sweet potatoes in a low oven at 300°F. The idea is that the low temperature allows the natural enzymes to break down the complex starches into simple sugars. The recipe also gives the option to sous-vide the whole sweet potatoes for two to four hours and then roast for another two hours to maximize the enzymatic process. I decided to stick to roasting to keep things simpler, as I had so many recipes going at once. 

While the sweet potatoes are roasting, you brown a stick of butter until nutty. Fresh thyme and/or sage is added, infusing the butter with even more flavor. 

After the sweet potatoes are done cooking, they’re peeled, added to the bowl of a stand mixer, then whipped with fresh ginger, the herbed brown butter, and a little sour cream. Everything is transferred to a casserole dish and baked until heated through. Once that’s done, you’ll crank the oven, top the casserole with mini marshmallows, then bake until the marshmallows are toasted.

Credit: Photo: Andrew Bui; Food Styling: Jessie YuChen

My Honest Review of Serious Eats’ Sweet Potato Casserole with Marshmallows

This was my front runner going into the competition, so I was really surprised when it was clearly the least favorite on the table. 

To start, I had trouble roasting the potatoes. The recipe calls for six pounds of sweet potatoes, which the recipe states should be six large sweet potatoes. Mine were a little larger, so I ended up with five sweet potatoes. I wrapped them in foil as indicated, but when I went to check them after two hours as instructed, they weren’t tender in the center. I let them go for another 45 minutes, and even then the largest was just barely cooked through. (The more tapered ends, however, were quite soft.)

The rest of the filling was fairly straightforward. The brown butter smelled delicious, and I opted to use all sage, as I find it to be the quintessential Thanksgiving herb. But when I went to pour it into the 2-quart casserole as indicated, I realized there was no way it was going to fit. Fortunately, I had an extra foil 9×13-inch pan on hand and I was able to use that. But I can definitely envision a situation on Turkey Day when you’re juggling multiple dishes, ready for the next step of your recipe, and the 9×13-inch you actually need is already filled with green bean casserole. 

Once the sweet potatoes were in the oven for their first bake, I realized the amount of marshmallows called for wasn’t going to be enough. There wasn’t really a way to scale up accurately without dimensions listed in the recipe, so I eyeballed it and added enough so that it looked like the photo. I turned up the oven, browned the ‘mallows, and was pleased to pull out a picture-perfect-looking casserole, despite the snafus. 

But digging into the dish, any confidence I had immediately went out the window. This didn’t taste at all like a sweet potato dish. At first, I was overwhelmed with sage. The more I ate, the more I realized there wasn’t much sweetness to the sweet potatoes at all. Perhaps my oven temperature was off and the enzymatic process didn’t happen as indicated, or maybe there were just too many savory ingredients mixed into the base. When topped with the sugary sweet marshmallows, the contrast was jarring.

Looking back at the headnotes, there’s a specific point where it mentions that there shouldn’t be “too much of a mismatch between the two parts — the juxtaposition makes extreme differences that much more glaring.” But to me and my testers, that’s exactly what happened here. Instead of the sweet potato’s natural charm and sass being celebrated, it was completely masked.

If You’re Making Serious Eats’ Sweet Potato Casserole with Marshmallows, a Few Tips

  1. Plan for plenty of time to roast the potatoes. Your potatoes should weigh no more than one pound each if possible.
  2. Use a combination of herbs. The recipe gives the option of using fresh thyme or sage, or a combination of both. Use a combination, or stick with thyme to avoid the sage overpowering things. 
  3. Go for a larger baking dish. Be prepared with a larger baking dish than what’s called for, and have extra mini marshmallows on hand for topping. 

Overall rating: 5/10