Sweet Potato Gratin with Roasted Chicken & Cheddar Cheese Sauce

There’s something about a bubbling gratin that instantly makes a night feel calmer. This one is especially cozy: sweet potatoes roasted just enough to start turning tender at the edges, juicy seasoned chicken, and a cheddar cheese sauce that’s creamy, sharp, and basically impossible not to “taste test” three times before it hits the oven.

It’s the kind of dish you make when you want comfort food that still feels a little put-together—perfect for a Sunday dinner, a chilly weeknight when you need extra warmth, or anytime you want leftovers that reheat like a dream. Once it’s baking, your kitchen smells like roasted goodness and melted cheese, and the top gets that golden, slightly crisp finish that makes everyone hover near the oven.

Ingredients

For the Gratin

2 large sweet potatoes, peeled and thinly sliced
2 tbsp olive oil
Salt and black pepper, to taste
1/2 tsp dried thyme (optional)

For the Roasted Chicken

2 boneless, skinless chicken breasts
1 tbsp olive oil
1/2 tsp garlic powder
1/2 tsp paprika
Salt and pepper, to taste

For the Cheddar Cheese Sauce

2 tbsp unsalted butter
2 tbsp all-purpose flour
1 1/2 cups whole milk, warmed
1 1/2 cups sharp cheddar cheese, shredded
Salt and pepper, to taste
Pinch of nutmeg (optional)

For Assembly

1/2 cup shredded cheddar cheese (for topping)
Fresh parsley, chopped (for garnish)

Instructions

1) Preheat and prep the dish

Set your oven to 400°F (200°C). Lightly grease a 9×13-inch baking dish and set it aside.

2) Roast the sweet potatoes

Toss the sweet potato slices with olive oil, salt, pepper, and thyme if you’re using it.
Spread them out on a baking sheet in a single layer (a little overlap is fine, but don’t pile them too high).
Roast for 15–20 minutes, just until they’re slightly tender—think “bendable,” not fully soft.

3) Roast the chicken

Rub the chicken breasts with olive oil, garlic powder, paprika, salt, and pepper.
Place them on another baking tray and roast for 20–25 minutes, or until cooked through.
Let them rest for 5 minutes (this keeps them juicy), then slice thinly or shred.

4) Make the cheddar cheese sauce

Melt butter in a saucepan over medium heat. Whisk in the flour and cook for about 1 minute—you’re just taking away the raw flour taste.
Slowly whisk in the warm milk, a little at a time, stirring the whole way so it stays silky.
Let it simmer for 2–3 minutes until it thickens into a creamy sauce.
Turn the heat low and stir in cheddar, salt, pepper, and nutmeg (if using). Stir until smooth and glossy.

5) Assemble the gratin

Lower your oven to 375°F (190°C).
In the greased baking dish:

Layer half the roasted sweet potatoes
Add half the chicken
Pour over a generous layer of cheese sauce

Repeat with the remaining sweet potatoes, chicken, and cheese sauce.
Finish with that extra 1/2 cup cheddar sprinkled across the top like a cozy blanket.

6) Bake until bubbly

Bake for 20–25 minutes, until the top is golden and the edges are bubbling happily.

7) Rest, garnish, and serve

Let it rest for 5 minutes before slicing—this helps it set up so you get those pretty layers.
Sprinkle with chopped parsley and serve warm.

Presentation (Little touches that make it feel fancy)

Go for clean layers: When you layer the sweet potatoes, slightly shingle them like cards. It looks gorgeous when you scoop it out.
Golden top hack: If you want extra browning, pop it under the broiler for 1–2 minutes at the end—just don’t walk away.
Serve it cozy-style: A wide spoon scoop on a plate, extra parsley, and a little cracked pepper on top makes it look chef-y in seconds.
Add something fresh on the side: A bright green salad or simple steamed green beans balances the richness perfectly.

Conclusion

This sweet potato gratin is comfort food that shows up dressed nicely. You get the natural sweetness of the potatoes, the savory roasted chicken, and that sharp cheddar sauce tying everything together in the creamiest way. It’s warm, filling, and feels like a hug in casserole form.

If you’re craving something cozy and melty soon—put this on your list for the next dinner you want to feel a little extra special.