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When the foil comes off, the sweet potatoes are tender but the sauce is still working its way around the layers. The uncovered stretch is when it bubbles at the edges and turns into the creamy, garlicky coating that makes Garlic Butter Scalloped Sweet Potatoes more than a stack of sliced vegetables.

I build the sauce separately before it goes into the baking dish. Butter and flour give the milk and cream a little structure, so the finished casserole doesn’t depend on the potatoes alone to thicken everything. Keep the slices even, let the sauce simmer until it lightly thickens, and you’ll have soft layers with a rich garlic-butter sauce clinging between them.

Why the Sauce Gets Thick Before It Ever Meets the Sweet Potatoes

Scalloped sweet potatoes need enough sauce to slip between the slices, but a thin pool of dairy can leave the casserole loose when you serve it. Here, the flour is cooked into butter first, then the milk and cream are whisked in gradually. That creates a smooth base with enough body to coat the layers instead of relying on the potatoes alone to thicken the pan.

The sauce shouldn’t be as thick as gravy before it goes into the oven. A gentle simmer for a few minutes is enough to make it lightly thickened; it will continue to cook around the potatoes as they soften. The cream brings richness, while whole milk keeps the sauce pourable. Together, they make a casserole that feels lush without turning into a heavy paste.

What the Sweet Potatoes, Garlic, and Dairy Bring to the Sauce

• Sweet potatoes — Choose firm potatoes without soft spots; they’ll peel and slice cleanly and hold their shape as they bake. Standard orange-fleshed sweet potatoes work well here, and there’s no need to seek out a specialty variety.
• Unsalted butter — It carries the garlic flavor and forms the base for the flour. Ordinary supermarket butter is a good fit; using unsalted also lets the kosher salt in the sauce stay in balance.
• Garlic — Freshly minced cloves give the butter a fragrant, savory flavor. Jarred minced garlic will work in a pinch, though its aroma is less sharp.
• All-purpose flour — This is the sauce’s thickener, not just a way to make the butter mixture look smooth. Whisk it in well so it cooks evenly before the dairy is added.
• Whole milk and heavy cream — Whole milk keeps the sauce fluid enough to pour, and heavy cream gives it its rounded, rich texture. Using both is what keeps the sauce from tasting thin or overly heavy.

From Garlic Butter to Tender, Bubbling Potato Layers

Cut and Set Up the Layers

Heat the oven to 375°F and grease a 9×13-inch baking dish with 1 tablespoon of butter. Peel the sweet potatoes and slice them into rounds. Keep the slices as consistent as possible so they soften at a similar pace. Set the prepared dish nearby before you make the sauce.

Wake Up the Garlic in Butter

Melt the remaining 4 tablespoons of butter in a medium saucepan over medium heat. Stir in the minced garlic and cook for 30 seconds, just until fragrant. The garlic should smell warm and savory, not toasted or brown. If it starts coloring quickly, lower the heat so it doesn’t turn bitter.

Whisk a Smooth, Lightly Thickened Sauce

Whisk the flour into the garlic butter and cook it for 1 minute. Gradually whisk in the milk and cream, keeping the whisk moving until the sauce is smooth. Add the salt and pepper, bring the sauce to a gentle simmer, and cook for 2 to 3 minutes while whisking. It’s ready when it has thickened lightly but still pours easily.

Bake Until the Knife Slides Through

Arrange the sweet potato rounds in overlapping layers in the greased dish, then pour the sauce evenly over them. Cover the dish tightly with foil and bake for 45 minutes. Uncover and bake for 20 to 30 minutes more, until a knife slides easily into the potatoes and the sauce bubbles at the edges. Let the casserole rest for 15 minutes before serving so the sauce can settle around the layers.

Two Useful Swaps for Garlic Butter Scalloped Sweet Potatoes

Questions That Come Up When Baking These Sweet Potatoes

Garlic Butter Scalloped Sweet Potatoes

Garlic butter scalloped sweet potatoes bake in a creamy sauce until the potatoes are tender and the edges are bubbling. Thin overlapping slices make this 9x13-inch casserole a hearty, savory side dish.

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Prep Time 15 minutes mins

Cook Time 1 hour hr 15 minutes mins

Resting 15 minutes mins

Total Time 1 hour hr 45 minutes mins

Servings: 8 servings

Course: Side Dish

Cuisine: American

Calories: 361

Ingredients Equipment Method Notes

Ingredients

  

• 5 tbsp unsalted butter divided
• 3 lb sweet potatoes peeled
• 4 cloves garlic minced
• 3 tbsp all-purpose flour
• 2 cup whole milk
• 1 cup heavy cream
• 1.5 tsp kosher salt
• 0.5 tsp black pepper

Equipment

• 1 9x13-inch baking dish

Method

 

1. Heat the oven to 375°F.
2. Grease a 9x13-inch baking dish with 1 tablespoon of the butter.
3. Slice the sweet potatoes into 1/8-inch-thick rounds.
4. Melt the remaining 4 tablespoons butter in a medium saucepan over medium heat.
5. Add the garlic and cook for 30 seconds until fragrant.
6. Whisk in the flour and cook for 1 minute.
7. Gradually whisk in the milk and cream until smooth.
8. Whisk in the salt and pepper.
9. Bring the sauce to a gentle simmer and cook for 2 to 3 minutes, whisking, until lightly thickened.
10. Arrange the sweet potato slices in overlapping layers in the prepared dish.
11. Pour the sauce evenly over the sweet potatoes.
12. Cover the dish tightly with foil and bake for 45 minutes.
13. Uncover and bake for 20 to 30 minutes, until a knife slides easily into the potatoes and the sauce is bubbling at the edges.
14. Let the casserole rest for 15 minutes before serving.

Notes

For even cooking, slice the sweet potatoes uniformly. Refrigerate leftovers for 3 to 4 days; freezing is not recommended because it can soften the texture. For a dairy-free variation, use unsweetened plant milk and a dairy-free butter alternative.