Sweet Onion Casserole Recipe

A savory and slightly sweet casserole featuring tender onions, rich cream, and a crunchy topping. Perfect as a side dish for any meal.


  • 6 large sweet onions (such as Vidalia), thinly sliced
  • 4 tablespoons butter
  • 1 cup heavy cream
  • 1 cup shredded cheddar cheese
  • 1/2 cup grated Parmesan cheese
  • 1 cup breadcrumbs (preferably panko)
  • 1 teaspoon salt
  • 1/2 teaspoon black pepper
  • 1 teaspoon fresh thyme leaves (optional)
  • Cooking spray or additional butter for greasing the baking dish


  1. Preheat the Oven:
  • Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with cooking spray or butter.
  1. Cook the Onions:
  • In a large skillet over medium heat, melt the butter.
  • Add the sliced onions and cook, stirring occasionally, until they are very soft and beginning to caramelize, about 20-25 minutes.
  1. Prepare the Casserole Base:
  • Once the onions are cooked, transfer them to the greased baking dish.
  • Pour the heavy cream evenly over the onions.
  • Sprinkle the shredded cheddar cheese and half of the grated Parmesan cheese over the onions.
  1. Prepare the Topping:
  • In a small bowl, combine the breadcrumbs, remaining Parmesan cheese, salt, black pepper, and fresh thyme leaves (if using).
  • Sprinkle the breadcrumb mixture evenly over the top of the casserole.
  1. Bake the Casserole:
  • Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the casserole is bubbly.
  1. Serve:
  • Remove from the oven and let it cool slightly before serving. Enjoy your sweet onion casserole as a delicious side dish!


  • For an extra creamy texture, you can mix 1/2 cup of sour cream into the onions before adding the cream and cheese.
  • To add a bit of heat, consider adding a pinch of red pepper flakes to the breadcrumb mixture.

Enjoy your sweet onion casserole!

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