Onions Au Gratin

Indulge in the rich, comforting elegance of Onions Au Gratin, a delightful recipe that transforms humble yellow onions into a gourmet masterpiece. This dish features tender, simmered onion halves smothered in a creamy, nutmeg-infused cheese sauce made with Gruyère and Parmesan, then topped with a golden, crispy breadcrumb crust. Perfectly baked to bubbling perfection, it delivers a balance of hearty flavors and textures that make it an irresistible side dish or vegetarian centerpiece. Easy to prepare in under an hour, this dish is ideal for holidays, dinner parties, or whenever you're craving something indulgent and savory. Garnished with fresh parsley for a pop of color and freshness, Onions Au Gratin is sure to impress with its elegant simplicity and bold flavors.

Nutriscore Rating: 61/100

Prep Time:20 mins

Cook Time:40 mins

Total Time:60 mins

Servings: 4

Ingredients

• 4 medium Yellow onions
• 3 tablespoons Unsalted butter
• 2 tablespoons All-purpose flour
• 1.5 cups Whole milk
• 0.5 teaspoons Salt
• 0.25 teaspoons Ground black pepper
• 0.125 teaspoons Ground nutmeg
• 1 cup Gruyère cheese, shredded
• 0.5 cups Parmesan cheese, grated
• 0.5 cups Breadcrumbs
• 1 tablespoon Olive oil
• 2 tablespoons Fresh parsley, chopped (optional)

Directions

Step 1

Preheat your oven to 375°F (190°C).

Step 2

Peel the onions and slice them in half crosswise. Remove a small slice from the bottom of each half so they sit flat.

Step 3

Place the onion halves cut side down in a large pot and cover with water. Bring to a boil and simmer for 8-10 minutes, until just tender but not falling apart.

Step 4

Drain the onions and carefully transfer them to a greased baking dish, cut side up.

Step 5

In a medium saucepan, melt the butter over medium heat. Stir in the flour and cook for 1-2 minutes, stirring constantly, to form a roux.

Step 6

Gradually whisk in the milk, ensuring there are no lumps. Cook, whisking constantly, until the sauce thickens, about 3-5 minutes.

Step 7

Stir in the salt, pepper, and nutmeg. Remove the saucepan from heat and mix in half of the Gruyère cheese and half of the Parmesan cheese until melted and smooth.

Step 8

Pour the cheese sauce evenly over the onions in the baking dish.

Step 9

In a small bowl, mix the breadcrumbs with the olive oil and the remaining Gruyère cheese and Parmesan cheese.

Step 10

Sprinkle the breadcrumb mixture evenly over the dish to form a topping.

Step 11

Bake in the preheated oven for 20-25 minutes, or until the topping is golden brown and crisp.

Step 12

Let the dish cool for 5 minutes, garnish with fresh parsley (if using), and serve warm.

Nutrition Facts

Serving size	1088.5 grams (1088.5g)

Amount per serving	% Daily Value*
Calories	1697

Total Fat 113.20g	145%
Saturated Fat 58.80g	294%
Polyunsaturated Fat 1.70g
Cholesterol 297mg	99%
Sodium 3668mg	159%
Total Carbohydrate 112.40g	41%
Dietary Fiber 10.20g	36%
Total Sugars 40.20g
Protein 74.30g	149%

Vitamin D 185IU	925%
Calcium 2107mg	162%
Iron 5mg	27%
Potassium 1331mg	28%

*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.

Source of Calories

Fat: 57.7%

Protein: 16.8%

Carbs: 25.5%