Description

A cozy, comforting gratin made with layers of thinly sliced sweet potatoes, hearty oats, fragrant sage, and melty cheese. Perfect as a vegetarian main or a hearty holiday side dish.

Ingredients

3 medium sweet potatoes, peeled and thinly sliced

1 cup rolled oats (not instant)

1 ½ cups grated sharp cheddar cheese (or any good melting cheese)

1 medium onion, thinly sliced

2 tablespoons fresh sage, chopped

1 clove garlic, minced

2 tablespoons olive oil

1 ½ cups milk (dairy or plant‑based)

1 tablespoon Dijon mustard

Salt and freshly ground black pepper to taste

2 tablespoons grated Parmesan cheese (optional, for topping)

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Instructions

Preheat the oven to 375°F (190°C) and lightly grease a 9×9‑inch baking dish with olive oil.
In a skillet, heat olive oil over medium heat and sauté the onion and garlic until soft and fragrant, about 5 minutes. Stir in chopped sage and cook for another minute.
In a bowl, whisk together the milk and Dijon mustard. Season with salt and pepper.
Layer half the sweet potato slices in the dish, slightly overlapping them. Sprinkle half the oats, half the onion-sage mixture, and half the grated cheese.
Repeat the layering with the remaining sweet potatoes, oats, onion-sage mixture, and cheese.
Pour the milk and mustard mixture evenly over the layers.
Cover the dish with foil and bake for 40 minutes.
Remove foil and bake for another 15–20 minutes, until the top is golden and bubbling and the sweet potatoes are fork-tender.
If using Parmesan, sprinkle it on during the last 5 minutes of baking.
Let the gratin rest for 10 minutes before slicing and serving.

Notes

Use plant-based milk and cheese for a vegan version.

Add sautéed spinach or kale between layers for extra nutrients.

Spice it up with red pepper flakes or smoked paprika.

Swap sage with rosemary or thyme for different flavor profiles.

Store leftovers in an airtight container in the fridge for up to 4 days or freeze for longer storage.

Prep Time: 15 minutes
Cook Time: 55 minutes
Category: Side Dish
Method: Baking
Cuisine: American

Nutrition

Serving Size: 1/6 of dish
Calories: 360
Sugar: 6g
Sodium: 400mg
Fat: 20g
Saturated Fat: 9g
Unsaturated Fat: 10g
Trans Fat: 0g
Carbohydrates: 34g
Fiber: 5g
Protein: 12g
Cholesterol: 35mg