Oniony Potatoes Au Gratin
Indulge in the creamy, cheesy perfection of Oniony Potatoes Au Gratin, a comforting casserole that elevates classic scalloped potatoes with the rich, savory sweetness of caramelized onions. Thinly sliced russet potatoes are layered with golden onions, a velvety cheese sauce made with Gruyère and sharp cheddar, and a fragrant hint of fresh thyme. The dish is finished with an option for a golden breadcrumb topping, adding a delightful crunch. Perfect for holidays, family dinners, or any special occasion, this easy-to-follow recipe combines simple ingredients with elevated flavors for a side dish that steals the spotlight. Serve warm and bask in the irresistible aroma of baked goodness straight from the oven!
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Recipe Information
Ingredients
- 4 large Russet potatoes
- 2 medium Yellow onion
- 6 tablespoons Unsalted butter
- 3 tablespoons All-purpose flour
- 2.5 cups Whole milk
- 0.5 cups Heavy cream
- 1.5 cups Shredded Gruyère cheese
- 1 cup Shredded sharp cheddar cheese
- 1.5 teaspoons Salt
- 0.5 teaspoons Ground black pepper
- 0.5 teaspoons Fresh thyme leaves
- 1 clove Garlic
- 1 tablespoon Olive oil
- 0.5 cup Breadcrumbs (optional)
Instructions
Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with butter or nonstick spray.
Peel the potatoes and slice them into 1/8-inch thick rounds using a mandolin or a sharp knife. Set aside in a bowl of cold water to prevent them from browning.
Peel and thinly slice the onions. Mince the garlic clove.
Heat 1 tablespoon of olive oil and 2 tablespoons of butter in a large skillet over medium heat. Add the onions and a pinch of salt, and cook, stirring occasionally, for 15-20 minutes until the onions are soft and golden brown. Stir in the minced garlic during the last minute of cooking. Remove from heat and set aside.
In a medium saucepan, melt the remaining 4 tablespoons of butter over medium heat. Whisk in the flour and cook for 1-2 minutes to form a roux, stirring constantly.
Gradually whisk in the milk and heavy cream, ensuring there are no lumps. Cook for 5-7 minutes, stirring frequently, until the mixture thickens slightly.
Remove the saucepan from heat and stir in the Gruyère cheese, sharp cheddar cheese, 1 teaspoon of salt, black pepper, and fresh thyme leaves. Mix until the cheese is fully melted and incorporated.
Drain the sliced potatoes and pat them dry with a clean kitchen towel.
Layer one-third of the sliced potatoes evenly in the bottom of the prepared baking dish. Spread one-third of the caramelized onions over the potatoes. Pour one-third of the cheese sauce over the onions. Repeat this layering process two more times, ending with the cheese sauce on top.
If using breadcrumbs, sprinkle them evenly over the top layer of cheese sauce.
Cover the dish with aluminum foil and bake in the preheated oven for 50 minutes.
Remove the foil and continue to bake for an additional 30-40 minutes, or until the top is golden brown and the potatoes are tender when pierced with a fork.
Allow the dish to rest for 10 minutes before serving. Sprinkle additional fresh thyme leaves as a garnish, if desired. Enjoy!
Nutrition Facts
Calories |
3557 | ||
|---|---|---|---|
% Daily Value* |
|||
| Total Fat | 196.3 g | 252% | |
| Saturated Fat | 115.8 g | 579% | |
| Polyunsaturated Fat | 2.0 g | ||
| Cholesterol | 560 mg | 187% | |
| Sodium | 5886 mg | 256% | |
| Total Carbohydrate | 335.5 g | 122% | |
| Dietary Fiber | 25.6 g | 91% | |
| Total Sugars | 52.7 g | ||
| Protein | 136.5 g | 273% | |
| Vitamin D | 7.6 mcg | 38% | |
| Calcium | 3316 mg | 255% | |
| Iron | 16.4 mg | 91% | |
| Potassium | 8148 mg | 173% | |
*The % Daily Value tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
