Ingredients:

  • 3 lbs Yellow Onions, peeled and sliced thickly (about 1/2 inch)
  • 3 Tbsp Extra Virgin Olive Oil
  • 1 tsp Kosher Salt
  • 1/2 tsp Freshly Ground Black Pepper
  • 4 Tbsp Unsalted Butter
  • 4 Tbsp All-Purpose Flour
  • 2 cups Whole Milk (warmed slightly)
  • Pinch Freshly Grated Nutmeg
  • 1 tsp Dijon Mustard
  • 1 cup Freshly Grated Parmesan Cheese (packed)
  • 1/2 cup Panko Breadcrumbs
  • 1 Tbsp Melted Butter (for topping)

Instructions:

  1. Preheat oven to 400°F (200°C). Toss sliced onions with olive oil, salt, and pepper directly in a large roasting pan.
  2. Roast onions for 35–40 minutes, stirring every 15 minutes, until they are deeply softened and beginning to brown around the edges. Remove from oven.
  3. While onions roast, prepare the béchamel base: Melt butter in a medium saucepan over medium heat. Whisk in flour (creating a roux) and cook for 1 minute until slightly nutty.
  4. Gradually whisk in the warm milk, ensuring no lumps form. Bring to a gentle simmer, whisking constantly, until the sauce thickens enough to coat the back of a spoon (about 5–7 minutes).
  5. Remove the sauce from the heat. Whisk in Dijon mustard and nutmeg. Stir in the grated Parmesan cheese until fully melted and smooth. Season carefully with salt and pepper.
  6. Gently fold the roasted onions into the Parmesan cream sauce until evenly coated. Transfer the mixture to a clean, oven-safe baking dish.
  7. If using the topping, toss Panko breadcrumbs with 1 Tbsp melted butter. Sprinkle evenly over the top of the onion mixture.
  8. Bake at 375°F (190°C) for 20–25 minutes, or until the sauce is bubbling and the topping is golden brown and crisp.
  9. Let the Roasted Parmesan Creamed Onions rest for 5–10 minutes before serving to allow the sauce to set slightly.