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5 from 2 votes

Sweet Onion Casserole with Crispy Topping

This Sweet Onion Casserole with Crispy Breadcrumbs Topping is a unique make ahead side dish. Onion is so overlooked as a vegetable, often it just added to dishes rather than being the star of the dish. This easy Thanksgiving side dish takes onions and turns them into the BEST kind of casserole - one that is packed wth flavor and goes with everything!
Prep Time10 mins
Cook Time55 mins
Total Time1 hr 5 mins
Course: Side
Cuisine: Modern Australian
Servings: 6 -8
Calories: 277kcal
Author: Claire | Sprinkles and Sprouts
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  • 2.5 lb onions
  • 1 stick butter
  • 1/2 tsp salt
  • 3/4 cup water
  • 2 tsp sugar
  • 2 tsp balsamic vinegar
  • 1 cup panko breadcrumbs
  • 1 tbsp olive oil
  • 1 tsp chopped chives
  • 1 tsp chopped parsley


  • If cooking and serving immediately pre-heat the oven to 350ºF/175ºC
  • Peel and finely slice the onions. (see note 1)
  • Heat the butter in a large dutch oven or high sided skillet.
  • When it has just melted add in the onions and salt then stir to coat everything in the butter.
  • Cook, uncovered over a low heat for 30 minutes until the onions are soft but not coloured.
  • Turn up the heat and add the water, sugar and balsamic vinegar.
  • Let the mixture bubble gently for 10-15 minutes until the liquid has evaporated and the onions are melting tender.
  • Transfer the onions to a casserole dish and either continue to the next step or keep refrigerated for up to 24 hours. (see below for more prepare ahead instructions)
  • heat the olive oil in a non-stick skillet and add in the breadcrumbs, cook over a medium heat until the breadcrumbs start to color. Remove the pan from the heat and immediately tip the crumbs into a cold bowl. This stops the breadcrumbs from burning.
  • Sprinkle the breadcrumbs over the hot onions and cook for 10 minutes to allow everything to meld together.
  • Sprinkle over the fresh herbs and serve.

To prepare ahead.

  • Cook the onions up to the stage where you place them in the casserole. Then cover tightly and refrigerate for up to 24 hours.
  • Prepare the breadcrumbs and store in an airtight container or ziplock bag for up to 5 days.

To re-heat.

  • Place the onions in the oven and cook for 20 minutes until hot, sprinkle over the breadcrumbs and cook for a further 10 minutes.
  • Alternatively reheat the inions in the microwave (around 7 minutes) and then cover with the breadcrumbs and bake for 10 minutes.
  • Sprinkle over the fresh herbs and serve.


  1. The quickest and easiest way to slice the onions is to use a slicer attachment on your food processor. You can also use a mandolin but please for the love of sam use the finger guard! Those blades are lethal! Obviously you can go old school and use a sharp knife. It is possible, but far more time consuming.


Calories: 277kcal | Carbohydrates: 26g | Protein: 3g | Fat: 18g | Saturated Fat: 10g | Cholesterol: 40mg | Sodium: 411mg | Potassium: 295mg | Fiber: 3g | Sugar: 10g | Vitamin A: 470IU | Vitamin C: 14mg | Calcium: 66mg | Iron: 0.9mg
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