Creamy Potato Casserole with Caramelized Onions and Parmesan – A Cozy Winter Supper

This cozy winter supper is all about simplicity: thinly sliced potatoes tucked into a glass casserole dish and drenched in one creamy pour-over made from heavy cream, caramelized onions, Parmesan, and fresh thyme. It bakes up into something between scalloped potatoes and a gratin—rich, golden, and deeply comforting. This is the kind of dish you slide into the oven on a cold night while the kids finish homework and the house starts to smell like a hug.

Serve these creamy baked potatoes alongside roasted chicken, meatloaf, or simple baked pork chops. A crisp green salad with a tangy vinaigrette or some steamed green beans helps balance the richness. For a cozy, all-in-one feel, add warm crusty bread to mop up the extra sauce and a side of applesauce or sliced oranges for a fresh, family-friendly touch.

Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch glass casserole dish with 1 tablespoon butter or cooking spray. Set aside.

Caramelize the onions: In a large skillet, melt 2 tablespoons butter over medium heat. Add the sliced onions and 1/2 teaspoon of the salt. Cook, stirring occasionally, for 20–25 minutes, lowering the heat if they start to brown too quickly. If they seem dry or start to scorch, add 1 tablespoon olive oil and a splash of water. Sprinkle in the optional 1 teaspoon sugar if you’d like to speed up caramelizing. Continue cooking until the onions are soft, golden brown, and sweet-smelling. Remove from heat and let cool slightly.

Make the creamy pour-over: In a medium bowl or large measuring cup with a spout, whisk together the heavy cream, 1 cup grated Parmesan, remaining 1 teaspoon salt, black pepper, and chopped thyme. Stir in the warm caramelized onions until everything is well combined. This is your one creamy pour-over mixture.

Prepare the potatoes: Peel the potatoes if you like (you can leave the skins on for more texture and nutrients). Slice them into thin rounds, about 1/8-inch thick, using a sharp knife or a mandoline. Try to keep the slices even so they cook at the same rate.

Layer the potatoes in the dish: Arrange the sliced potatoes evenly in the greased glass casserole dish, spreading them out so there are no big clumps. It doesn’t have to be perfect—just aim for an even layer or two so the creamy pour-over can reach everything.

Pour the creamy mixture over the potatoes: Give the creamy pour-over a quick stir, then slowly pour this one creamy mixture all over the raw potatoes in the glass casserole dish, making sure to distribute the onions and herbs as evenly as you can. Gently shake the dish or use a spoon to nudge the potatoes so the cream seeps down between the slices.

Top and cover: Sprinkle the remaining 2 tablespoons grated Parmesan over the top. Cover the dish tightly with foil so the potatoes can steam and soften without drying out.

Bake until tender: Place the covered glass casserole dish on the middle rack of the preheated oven. Bake for 45–55 minutes, or until the potatoes are fork-tender when you poke the center with a knife.

Brown the top: Remove the foil and continue baking for another 15–20 minutes, or until the top is bubbly, lightly golden, and the edges are browned and crisp in spots.

Rest and serve: Let the potatoes rest for at least 10 minutes before serving so the creamy sauce can thicken slightly. Spoon into bowls or onto plates and serve warm for an absurdly satisfying, cozy winter supper.

Tips and Variations

• For picky eaters: Finely chop the caramelized onions so they almost melt into the sauce. Kids often accept the flavor more easily when they don’t see big onion pieces.
• Herb substitution: If someone in your house doesn’t love thyme, swap it for chopped parsley or leave the herbs out and finish with a sprinkle of dried Italian seasoning on just half the dish.
• Lighter version: Use 1 cup heavy cream and 1 cup whole milk instead of all cream. It will be slightly less rich but still comforting.
• Extra cheesiness: Mix in 1/2 cup shredded mozzarella or mild cheddar with the Parmesan in the pour-over.
• Make ahead: Assemble the dish up to the point of baking, cover, and refrigerate for up to 24 hours. Add an extra 10–15 minutes to the covered baking time if it goes into the oven cold.
• One-pan feel: Tuck in a layer of thinly sliced ham or cooked crumbled bacon between the potatoes before you pour on the cream.
• Vegetarian option: Add a layer of thinly sliced mushrooms or blanched broccoli florets under the creamy pour-over.
• Dried thyme: If you don’t have fresh thyme, dried thyme works well—just use about half the amount, as dried herbs are stronger.

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