Onion Sandwich Au Gratin
Indulge in the savory decadence of Onion Sandwich Au Gratin, a comforting baked dish that transforms humble ingredients into a gourmet masterpiece. Layers of golden, caramelized yellow onions are nestled between toasted slices of rustic bread and smothered with creamy Dijon-infused sauce. Topped with nutty Gruyere cheese and a crisp panko-Parmesan breadcrumb crust, this casserole-style take on the classic sandwich offers a rich, cheesy bite with every forkful. Perfect for dinners or an impressive brunch centerpiece, this recipe is simple yet elegant, with only 20 minutes of prep time. Finished with a sprinkle of fresh parsley, this crowd-pleaser guarantees a golden, bubbling delight straight out of your oven.
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Recipe Information
Ingredients
- 4 medium Yellow onions
- 3 tablespoons Unsalted butter
- 1 tablespoon Olive oil
- 1 teaspoon Salt
- 0.5 teaspoon Black pepper
- 1 teaspoon Granulated sugar
- 8 slices Rustic bread slices
- 2 cups Gruyere cheese
- 0.5 cup Heavy cream
- 1 tablespoon Dijon mustard
- 1 minced Garlic clove
- 0.5 cup Panko breadcrumbs
- 2 tablespoons Fresh parsley
- 0.25 cup Parmesan cheese
Instructions
Preheat your oven to 400°F (200°C) and grease a large baking dish with butter or cooking spray.
Peel and thinly slice the yellow onions.
Heat 2 tablespoons of butter and the olive oil in a large skillet over medium heat. Add the onions, salt, and pepper, and cook, stirring occasionally, for about 15 minutes until they soften.
Add granulated sugar to the onions and continue cooking for another 5-7 minutes until they are golden brown and caramelized. Remove from heat and set aside.
Toast the bread slices lightly under a broiler or in a toaster oven until just crisp. Set them aside on a wire rack to cool.
In a small saucepan, heat the heavy cream over low heat. Stir in Dijon mustard and the minced garlic. Allow it to warm through for about 2-3 minutes and set aside.
Grate the Gruyere cheese and set aside 1/2 cup for the topping.
To assemble the sandwiches, layer half the bread slices in the prepared baking dish. Top each slice with a generous amount of caramelized onions and sprinkle 1.5 cups of the Gruyere cheese over them.
Place the remaining bread slices on top to form sandwiches. Spoon the warmed cream mixture evenly over the sandwiches, ensuring it soaks through the bread.
Sprinkle the reserved Gruyere cheese over the top of the sandwiches.
In a small bowl, combine the panko breadcrumbs, chopped parsley, Parmesan cheese, and the remaining tablespoon of melted butter. Mix well and sprinkle evenly over the top of the dish.
Bake in the preheated oven for 15-20 minutes, or until the top is golden brown and bubbly.
Allow the dish to cool slightly before serving. Garnish with additional parsley, if desired.
Nutrition Facts
Calories |
3478 | ||
|---|---|---|---|
% Daily Value* |
|||
| Total Fat | 195.8 g | 251% | |
| Saturated Fat | 101.9 g | 510% | |
| Polyunsaturated Fat | 1.3 g | ||
| Cholesterol | 505 mg | 168% | |
| Sodium | 6240 mg | 271% | |
| Total Carbohydrate | 293.4 g | 107% | |
| Dietary Fiber | 17.1 g | 61% | |
| Total Sugars | 32.9 g | ||
| Protein | 131.2 g | 262% | |
| Vitamin D | 0.0 mcg | 0% | |
| Calcium | 3010 mg | 232% | |
| Iron | 14.8 mg | 82% | |
| Potassium | 1143 mg | 24% | |
*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.
