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Sweet Onion Casserole

Posted on March 2, 2025

Sweet Onion Casserole is a rich, comforting side dish that combines the natural sweetness of onions with a creamy, cheesy sauce and a crunchy topping. It’s a great side for family dinners, holiday meals, or anytime you want something a little different but still delicious. The onions soften during cooking, and their sweetness shines through, while the cheese and breadcrumbs give it a savory balance.

Here’s an easy recipe for Sweet Onion Casserole:

Sweet Onion Casserole Recipe

Ingredients:

  • 4 large sweet onions (Vidalia or Walla Walla onions work great)
  • 2 tbsp unsalted butter
  • 1 cup sour cream
  • 1 cup mayonnaise
  • 2 cups shredded cheddar cheese (or a mix of cheddar and mozzarella)
  • 1/2 tsp garlic powder
  • 1/2 tsp salt
  • 1/4 tsp black pepper
  • 1/2 cup panko breadcrumbs (for topping)
  • 2 tbsp melted butter (for topping)
  • 1 tbsp fresh parsley (optional, for garnish)

Instructions:

Step 1: Prepare the Onions

  1. Peel and slice the onions thinly. You want them to be evenly sliced so they cook uniformly.
  2. In a large skillet, melt 2 tablespoons of butter over medium heat. Add the sliced onions and sauté them for about 10-12 minutes, stirring occasionally, until they’re soft and slightly caramelized. You want to bring out the sweetness in the onions.

Step 2: Mix the Casserole Filling

  1. In a large bowl, combine the sour cream, mayonnaise, shredded cheese, garlic powder, salt, and pepper. Stir until smooth and well-combined.
  2. Once the onions have cooked down and softened, add them to the cheese mixture and stir to combine. Make sure the onions are evenly coated in the creamy mixture.

Step 3: Assemble the Casserole

  1. Preheat your oven to 350°F (175°C).
  2. Grease a 9×9-inch baking dish (or similar-sized dish) with a little butter or non-stick spray.
  3. Spoon the onion mixture into the prepared baking dish, spreading it out evenly.

Step 4: Add the Topping

  1. In a small bowl, combine the panko breadcrumbs with the melted butter. Stir to coat the breadcrumbs evenly.
  2. Sprinkle the breadcrumb mixture evenly over the top of the casserole.

Step 5: Bake

  1. Bake the casserole for about 30-35 minutes, or until the top is golden brown and the casserole is bubbly.
  2. If you want the topping to be extra crispy, you can broil it for the last 2-3 minutes of cooking. Just keep an eye on it so it doesn’t burn!

Step 6: Garnish and Serve

  1. Once baked, remove the casserole from the oven and let it cool for a few minutes before serving.
  2. Garnish with fresh parsley if desired, for a pop of color.

Tips & Variations:

  • Add some protein: You can add cooked chicken, sausage, or even bacon to make the casserole heartier.
  • Cheese options: If you want a different cheese flavor, try using Gruyère, Swiss, or Parmesan in place of the cheddar.
  • Veggie add-ins: Try adding some spinach, mushrooms, or broccoli to the casserole to make it even more filling and nutritious.
  • Spicy twist: Add a pinch of cayenne pepper or a few jalapeño slices for some heat.
  • For a lighter version: You can use Greek yogurt instead of sour cream and light mayonnaise for a lighter version.

Storage:

  • Refrigeration: Store leftovers in an airtight container in the fridge for up to 3-4 days.
  • Freezing: This casserole can be frozen before baking. Assemble the casserole, cover tightly, and freeze for up to 3 months. When ready to bake, thaw in the fridge overnight and bake as directed, adding an extra 10-15 minutes if needed.

This Sweet Onion Casserole is a great way to enjoy the natural sweetness of onions in a savory, cheesy dish that’s perfect as a side for any meal. It’s rich, creamy, and comforting, with a lovely crunch from the breadcrumb topping.

Let me know if you want more casserole recipes or variations!

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