Sweet Potato Au Gratin

This savory sweet potato au gratin brings together tender slices of sweet potato layered with a creamy herb and cheese sauce, then finished with a golden, crisp breadcrumb topping that draws raves every time I serve it. Whenever my family wants something a little extra special on the side, this is the dish I reach for. Each bite is perfectly balanced between the natural sweetness of the potatoes and the rich flavors from cheese and fresh herbs.

As the gratin bakes, your kitchen fills with the most comforting aroma from rosemary, garlic, and browned cheese. One year I brought it to Thanksgiving and it became the most requested dish for every family event after that.

Ingredients

• Sweet potatoes: about four or five pounds I look for firm and evenly sized potatoes for easy slicing and uniform cooking
• Parmesan cheese: adds sharp nutty flavor and melts beautifully I recommend grating your own for the best taste
• Heavy cream: gives the sauce its signature richness and velvety texture seek out cream with no added thickeners
• Fresh sage: delivers an earthy woodsy note choose leaves that are fragrant and free of brown spots
• Fresh rosemary: bright herbaceous flavor use only the tender sprigs for best flavor and easier chopping
• Garlic cloves: lend warmth and depth use fresh not pre-minced for maximum aroma
• Nutmeg: a small pinch rounds out the flavors with a subtle sweetness
• Salt and black pepper: both matter for seasoning every layer
• Panko breadcrumbs: give the topping that signature crunch look for unseasoned plain panko for best results
• Paprika: this brings a gentle smokiness and rich color try to find sweet Hungarian paprika
• Onion powder and garlic powder: add savory complexity without overpowering
• Cayenne: delivers just a hint of heat do not skip unless you are very spice averse
• Olive oil: helps the breadcrumbs toast up super crisp choose extra virgin if possible
• Butter: for greasing the baking dish so nothing sticks and you get golden edges

Step-by-Step Instructions

Prep the Sweet Potatoes:

Peel the sweet potatoes thoroughly then use a mandolin or sharp knife to slice them into even rounds about one eighth inch thick Aim for thin and uniform slices to ensure the casserole bakes evenly

Prepare the Baking Dish:

Generously butter your gratin or casserole dish then sprinkle a couple of tablespoons of Parmesan cheese evenly across the bottom This both flavors the base and helps prevent sticking

Layer the Potatoes and Season:

Arrange a layer using one third of the sweet potatoes slightly overlapping the slices Season with a quarter teaspoon salt and a few grinds of black pepper This step provides seasoning all the way through the dish

Make the Herb Cream:

In a medium saucepan gently heat the heavy cream with chopped sage fresh rosemary minced garlic nutmeg and a pinch of salt Bring just to a low boil over medium heat then reduce to a simmer Cook another ten minutes until the herbs are fragrant and the cream reduces by about one fourth Strain if you want a smoother sauce

Temper and Mix with Eggs:

Crack eggs into a medium bowl and whisk lightly While whisking slowly pour in the hot cream mixture This keeps the eggs from scrambling and thickens the sauce later

Layer Potatoes Cheese and Cream:

Pour a third of the cream mixture over your first potato layer Sprinkle with a third of the remaining Parmesan cheese Repeat with two more layers for a total of three fully stacked layers

Bake Covered:

Cover the dish tightly with foil Bake at four hundred degrees Fahrenheit for forty minutes Slowly baking covered ensures the potatoes turn soft but the topping stays crisp for later

Make the Breadcrumb Topping:

While baking stir together panko breadcrumbs remaining Parmesan cheese paprika onion powder garlic powder cayenne a pinch of salt and olive oil in a bowl This mixture should look like damp sand

Add Crunch and Finish Baking:

Carefully remove foil and sprinkle the breadcrumb mixture over the baked potatoes Return dish to the oven uncovered Bake another twenty to twenty five minutes until browned and bubbly The topping should be crisp and deeply golden

Cool and Serve:

Let the au gratin rest out of the oven for at least fifteen minutes before slicing This allows it to hold together when served

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The grace note in this recipe comes from the fresh sage which perfumes the whole dish with a toasty herbal note It always reminds me of my grandmother’s Thanksgiving table and brings that sense of celebration to even the most ordinary weeknight

Storage Tips

Sweet potato au gratin stores beautifully in the fridge Let leftovers cool completely then cover tightly and chill for up to four days To reheat cover with foil and warm in a three hundred fifty degree oven until hot throughout This keeps the topping crisp

Ingredient Substitutions

You can swap half the sweet potatoes for Yukon gold potatoes for extra earthiness or use Gruyere in place of Parmesan for a more pronounced cheesy flavor If you cannot find fresh herbs dried can work in a pinch but use half the amount since they are stronger

Serving Suggestions

This dish is a showstopper alongside roast chicken turkey or beef It also makes a fantastic vegetarian entrée with a crisp salad on the side I sometimes serve it with sautéed greens to balance the flavors

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Cultural Context

Au gratin is a classic technique that originated in French cuisine meaning a dish baked with a crispy top usually breadcrumbs and cheese Sweet potatoes bring an American regional twist making this recipe both traditional and updated

Frequently Asked Questions

→ How do you achieve evenly sliced sweet potatoes?

Using a mandolin or sharp knife ensures consistent, thin rounds for even baking and texture.

→ What herbs pair best with sweet potatoes in this dish?

Fresh sage and rosemary complement the natural sweetness, infusing each bite with savory depth.

→ Can I substitute panko crumbs?

Regular breadcrumbs can be used, but panko provides a crispy, light crunch to the topping.

→ How do you prevent the dish from being watery?

Simmering the cream mixture reduces moisture, and baking uncovered allows excess liquid to evaporate.

→ What is the best way to reheat leftovers?

Warm leftovers in a 350°F oven until heated through, which revives the topping's crispness.