Parmesan Onion Bake
Indulge in the rich, savory goodness of Parmesan Onion Bake—a comforting casserole that transforms sweet onions into a mouthwatering side dish. Featuring tender, golden-soft onions layered with a velvety Parmesan cream sauce and topped with a golden panko breadcrumb crust, this recipe is the ultimate crowd-pleaser. Perfect for holidays, potlucks, or family dinners, it delivers bold flavor with simple ingredients like sweet onions, grated Parmesan, and a hint of Italian seasoning. Ready in under an hour, this easy baked onion casserole pairs beautifully with roasted meats, hearty salads, or crusty bread. Garnished with fresh parsley for a pop of color, it's a warm, cheesy delight you'll return to again and again!
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Recipe Information
Ingredients
- 3 large Sweet onions (e.g., Vidalia or yellow onions)
- 3 tablespoons Unsalted butter
- 2 tablespoons All-purpose flour
- 1.5 cups Whole milk
- 1 cup Grated Parmesan cheese
- 1 teaspoon Salt
- 0.5 teaspoon Black pepper
- 0.5 teaspoon Italian seasoning
- 0.5 cup Panko breadcrumbs
- 1 tablespoon Olive oil
- 2 tablespoons Fresh parsley (optional, for garnish)
Instructions
Preheat your oven to 375°F (190°C) and lightly grease an 8x8-inch baking dish or similar-sized casserole dish.
Peel and slice the sweet onions into 1/4-inch thick rings, separating the layers.
Melt 2 tablespoons of unsalted butter in a large skillet over medium heat. Add the sliced onions and cook for about 10 minutes, stirring occasionally, until softened and lightly golden. Remove from heat and set aside.
In a medium saucepan, melt the remaining 1 tablespoon of butter over medium heat. Whisk in the flour and cook for 1 minute, stirring constantly to create a roux.
Gradually pour in the milk while whisking constantly to prevent lumps. Cook the mixture for 3-4 minutes, or until it thickens into a creamy sauce.
Stir in 3/4 cup of grated Parmesan cheese, salt, black pepper, and Italian seasoning. Mix until the cheese is fully melted and incorporated. Remove from heat.
Spread half of the cooked onions evenly in the prepared baking dish. Pour half of the Parmesan cream sauce over the onions. Repeat with the remaining onions and sauce, spreading evenly.
In a small bowl, combine the panko breadcrumbs, remaining 1/4 cup of Parmesan cheese, and olive oil. Stir until the breadcrumbs are evenly coated.
Sprinkle the breadcrumb mixture over the top of the creamy onions in the baking dish.
Bake uncovered in the preheated oven for 25-30 minutes, or until the top is golden and bubbling.
Remove from the oven and let sit for 5 minutes before serving. Garnish with fresh parsley, if desired.
Nutrition Facts
Calories |
239 | ||
|---|---|---|---|
% Daily Value* |
|||
| Total Fat | 14.3 g | 18% | |
| Saturated Fat | 7.9 g | 40% | |
| Polyunsaturated Fat | 0.0 g | ||
| Cholesterol | 35 mg | 12% | |
| Sodium | 654 mg | 28% | |
| Total Carbohydrate | 19.5 g | 7% | |
| Dietary Fiber | 1.7 g | 6% | |
| Total Sugars | 7.4 g | ||
| Protein | 9.5 g | 19% | |
| Vitamin D | 0.9 mcg | 4% | |
| Calcium | 246 mg | 19% | |
| Iron | 0.9 mg | 5% | |
| Potassium | 221 mg | 5% | |
*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.
