Scalloped Onions are a delicious side dish of sliced onions smothered in a rich and creamy Béchamel sauce and then baked to perfection.
Tired of the same old roasted potatoes or steamed vegetables? Often overlooked or used only as an aromatic in cooking, onions can be the star of a creamy casserole.
Sweet but savory, these Scalloped Onions will melt in your mouth and are a great accompaniment to any roasted meat.
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About This Recipe
This recipe was inspired by combining the ideas behind the casserole "Tennessee Onions, "Creamed Pearl Onions" (which are spectacular for steak dinners and holidays), and "Scalloped Potatoes."
The recipe is essentially an easy-to-make Béchamel sauce loaded with sliced, sweet yellow onions that are par-baked. Par-baking accomplishes two tasks:
- The sliced onions are more easily separated into rings.
- The onion's flavor becomes sweeter and less sharp.
I love the beautiful way this casserole looks. Although you could simply slice the onions and mix them into the sauce, and then bake them, I love stacking the onion rings so that they look like roses nestled in the sauce.
To finish off the casserole, I generally reserve a pinch each of the freshly ground black pepper and nutmeg and sprinkle them over the onions before baking. Lastly, a generous dusting of thyme leaves makes a gorgeous garnish before serving. Doesn't this sound delicious and beautiful? Great!
So, let's cook!
Ingredient Notes
Here's what you need:
- Yellow Onions - I prefer to use yellow onions, but you can use red, too. Do not use white onions as they have a sharp flavor.
- Salted Butter - Salted butter is best, but you can use unsalted butter and add an extra ¼ teaspoon of salt when making the Béchamel sauce.
- Wondra Flour - Wondra is a flour specifically milled for use in making sauces and gravies. If you do not have Wondra you can use all-purpose flour.
- Whole Milk - Whole milk has the best flavor for making creamed dishes.
- Heavy Cream - Heavy cream makes a deliciously rich Béchamel sauce.
- Salt - Just plain salt from the round blue box works great.
- Black Pepper - I always use freshly ground black pepper. It's aroma and flavor are pleasantly sharp and flowery.
- Ground Nutmeg - You can use pre-ground nutmeg, but fresh will be more fragrant with lemon overtones.
- Grated Romano Cheese - Romano cheese makes the sauce savory and delicately cheesy, letting the onions be the star of the dish.
- Fresh Thyme Leaves - Fresh thyme is wonderful with onions. However, you can use a small amount of dried if fresh is not available.
- Butter-Flavored Non-Stick Cooking Spray - I love using a butter-flavored cooking spray to grease the dish, and I also use a light spray on the onions before they are parbaked.
Please see the recipe card for the exact quantities.
How to Make Scalloped Onions
Prepare the Onions. Preheat an oven to 350°F/177°C.
Peel the onions and slice them, crosswise, 1” thick. Place the sliced onions on a parchment-covered baking sheet and spray with butter-flavored cooking spray. Lightly season with salt and pepper, if desired.
Par-bake for 15 minutes to slightly soften the onions and remove bitterness. Remove from oven and let cool while making the Béchamel sauce. Separate the cooled slices into groups of rings that look like roses.
Make Béchamel Sauce. In a heavy-bottomed medium-sized saucepan, melt the butter over medium-low heat. Add the flour. Stir and cook the butter and flour for 3 to 4 minutes until the flour is fully incorporated into the butter and well-cooked but not brown.
Whisk in the milk and heavy cream, and stir well to avoid lumps. Cook over medium heat until the sauce comes to a simmer and has thickened.
Immediately add salt, freshly ground black pepper, nutmeg, and Romano cheese. Taste and adjust seasoning if needed.
Assemble the Casserole. Grease the bottom and sides of a 10” x 8” casserole or baking dish with butter-flavored cooking spray. Pour the Béchamel sauce into the prepared dish. Arrange the par-baked sliced onions in the pan to make rosettes by placing smaller rings inside larger ones.
Bake. Bake the uncovered casserole for 25 minutes or until hot and bubbly. Then broil on high for 3 to 5 minutes or until the onions are slightly browned.
Garnish with fresh thyme leaves or chopped parsley. Serve and Enjoy!
My Top Tip
♡ Don't skip par-baking the onions. Not only are the onions easier to separate into rings, but they also become less sharp in flavor.
Make-Ahead, Storage, & Reheating Instructions
- Make-Ahead: Assemble this casserole up to baking it and cover it with aluminum foil. Bring the scalloped onion casserole to room temperature before baking it. It may need to bake longer.
- Refrigeration: Store leftovers in a sealed container for up to 3 days.
- Freezing: Do not freeze. Because this casserole contains dairy it will not freeze well.
- Reheating: Reheat gently in the microwave or the oven.
♡ Did you love this recipe for Scalloped Onions? Please leave a 🌟 star rating and let me know how things went in the ✍ comments below. Thanks for visiting!
📖 Recipe
Scalloped Onions
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Ingredients
- Butter-Flavored Non-Stick Cooking Spray
- 3 Pounds Yellow Onions, Peeled and Sliced 1” Thick
- 4 Tablespoons Salted Butter
- 4 Tablespoons Wondra Flour or All-Purpose Flour
- 2 Cups Whole Milk
- 1 Cup Heavy Cream
- ½ Teaspoon Salt
- ½ Teaspoon Black Pepper, Freshly Ground
- ½ Teaspoon Ground Nutmeg
- ⅓ Cup Grated Romano Cheese
- 1 Tablespoon Fresh Thyme Leaves, or Chopped Parsley
Instructions
- Prepare the Onions. Preheat an oven to 350°F/177°C. Peel the onions and slice them, crosswise, 1” thick. Place the sliced onions on a parchment-covered baking sheet and spray with butter-flavored cooking spray. Lightly season with salt and pepper, if desired. Par-bake for 15 minutes to slightly soften the onions and remove bitterness. Remove from oven and let cool while making the Béchamel sauce. Separate the cooled slices into groups of rings that look like roses.3 Pounds Yellow Onions, Butter-Flavored Non-Stick Cooking Spray
- Make Béchamel Sauce. In a heavy-bottomed medium-sized saucepan, melt the butter over medium-low heat. Add the flour. Stir and cook the butter and flour for 3 to 4 minutes until the flour is fully incorporated into the butter and well-cooked but not brown.Whisk in the milk and heavy cream, and stir well to avoid lumps. Cook over medium heat until the sauce comes to a simmer and has thickened.Immediately add salt, freshly ground black pepper, nutmeg, and Romano cheese. Taste and adjust seasoning if needed.4 Tablespoons Salted Butter, 4 Tablespoons Wondra Flour or All-Purpose Flour, 2 Cups Whole Milk, 1 Cup Heavy Cream, ½ Teaspoon Salt, ½ Teaspoon Black Pepper, ½ Teaspoon Ground Nutmeg, ⅓ Cup Grated Romano Cheese
- Assemble the Casserole. Grease the bottom and sides of a 10” x 8” casserole or baking dish with butter-flavored cooking spray. Pour the Béchamel sauce into the prepared dish. Arrange the par-baked sliced onions in the pan to make rosettes by placing smaller rings inside larger ones.
- Bake. Bake the uncovered casserole for 25 minutes or until hot and bubbly. Then broil on high for 3 to 5 minutes or until the onions are slightly browned. Garnish with fresh thyme leaves or chopped parsley. Serve and Enjoy!1 Tablespoon Fresh Thyme Leaves
Nutrition
Per 1 serving. All nutritional information on this site is an estimate. Your results may vary.
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Jan Nunes says
We love serving these creamy beautiful onions with Baked Potatoes and a Standing Rib Roast. They are amazing with the meat or on top of a baked potato.