Sourdough Green Bean Casserole

This sourdough green bean casserole features sourdough started in both a rich mushroom gravy and a crispy onion topping! Add in crisp-tender green beans and you’ve got a delicious family-friendly dish packed with phenomenal sourdough flavor.

Course Side Dish

Cuisine American

Keyword Sourdough Discard

Prep Time 1

Cook Time 20

Total Time 1 20

Servings

Calories 189kcal

Author Kate Freebairn

Equipment

Baking Sheet
Parchment Paper
Large Pot
Medium Saucepan
9" x 13" baking dish
Wooden Spoon
Whisk

Ingredients

Sourdough Onion Topping Ingredients

1 Onion medium size, sliced
100 g Sourdough Starter or discard
1 Egg
15 g Butter melted
2 g Salt (about ½ teaspoon, plus more for sprinkling)
60 g Breadcrumbs
30 g Parmesan Cheese grated

Casserole Ingredients

750 g Green Beans trimmed and cut into bite-sized pieces
60 g Butter plus more for greasing the dish
300 g Chopped Mushrooms
3 Garlic Cloves minced
5 g Salt plus more for the blanching water
120 g Sourdough Starter or discard
300 g Chicken Stock
360 g Milk
1 tsp Red Wine Vinegar or cider vinegar
1 tsp Worcestershire Sauce
1 tsp Soy Sauce
1 pinch Ground Nutmeg
¼ tsp Black Pepper

Instructions

Make The Sourdough Onion Topping

Line a baking sheet with parchment paper and preheat the oven to 350ºF/180ºC.
Whisk the sourdough starter, egg, melted butter, and salt in a small bowl. Next, you’ll mix the breadcrumbs and Parmesan together.
Coat the onions in the sourdough-egg mixture, then dredge in the breadcrumbs and Parmesan. Place on the prepared baking sheet and continue until all the onions are done.
Place in the oven and bake for 10 minutes. Use a spatula to flip the onions and bake for another 10 to 15 minutes, until golden brown. Set aside until the green beans and mushroom gravy are ready.

Prepare The Casserole

Bring a large pot of well-salted water to a boil with an ice bath nearby. Once the water is boiling, add the green beans and cook for 4 to 5 minutes, until tender. Immediately transfer beans to the ice bath. Once the beans are chilled, drain and set aside.
Make the mushroom gravy by melting the butter over medium-high heat in a medium saucepan. Add the chopped mushrooms and cook, stirring occasionally, until they start to brown and the liquid has cooked off, 8 to 10 minutes. Add the minced garlic and salt, stir, and cook until the garlic softens a bit.
Add the sourdough starter and stir to coat the mushrooms. Cook for 2 minutes.
Gradually add the stock, stirring and scraping up the browned bits from the bottom of the pan with a wooden spoon. Add the milk and bring to a simmer, stirring all the while. Turn the heat down to medium and continue to stir until the sauce is thick and creamy and coats the back of a spoon. Remove from heat and add the vinegar, Worcestershire sauce, soy sauce, black pepper, and nutmeg.
To assemble the casserole, add the green beans and about ⅓ of the sourdough onion-breadcrumb topping to a greased 9” x 13” baking dish. Stir lightly to distribute the onions amongst the green beans. Pour the mushroom gravy on top and stir until the green beans are nicely coated. Add the remaining crunchy onion topping, covering the top of the casserole evenly.
Bake the casserole for about 20 minutes, until the sourdough mushroom gravy is piping hot and bubbling, and the top is a crunchy dark golden brown. Serve immediately.

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