String Bean and Mushroom Casserole

String Bean Casserole is a tasty vegetarian dish made with fresh green beans, white sauce, mushrooms, onions, garlic, thyme, nutmeg, and ciabatta bread. The vegetables are sauteed and mixed with bechamel sauce, topped with torn ciabatta bread, and then baked. The bread gets crispy and the sauce is bubbly. This is the perfect side dish or main meal.

Jump to:

• What is String Bean Casserole? 
• Ingredients: 
• How to make string bean casserole: 
• Tips for success: 
• What can I top this casserole with? 
• Can I make this string bean casserole in an instant pot?  
• What other vegetables can I add to this dish?   
• How to store:
• FAQs:
• String Bean and Mushroom Casserole

What is String Bean Casserole? 

This recipe for green bean casserole is simple and can be served for special occasions like Thanksgiving or for weeknight dinners. Making this casserole from scratch is easy and will be on your dinner table in just 45 minutes. 
It’s made without soup and instead, the creaminess comes from jarred or homemade bechamel sauce. If you make it yourself, that makes this dish even healthier. This spin on a traditional dish will have you declaring this is definitely the better option.  

Ingredients: 

• 1 pound (500 g) string beans: You can find fresh green beans in the produce section of the grocery store when they’re in season. 
• 1⁄2 cup chicken stock: Use homemade stock or the best you can find at the grocery store. 
• 1 ½  cup bechamel sauce: You can use jarred bechamel sauce or make your own white sauce at home. 
• 2 cups cremini mushrooms, sliced: Be sure to wash the dirt from the mushrooms before slicing them. 
• 1 onion: White onions hold up best in casseroles. 
• 2 garlic cloves, minced: Check that the garlic is fresh and not dry after peeling them. 
• 1 teaspoon dried thyme: You can use fresh or dried thyme in this dish. 
• 1⁄2 teaspoon nutmeg: Dried and grated nutmeg adds a fun flavor twist to this casserole. 
• salt and pepper: A little seasoning brings out the other flavors. 
• Ciabatta bread: You can make your own ciabatta or buy some from a bakery.

How to make string bean casserole: 

Video Recipe:

Here’s a brief overview of how to make this dish. See the recipe card below for the specific recipe instructions. 

1. Preheat the oven to 400F/200C.

2. Use some olive oil to saute sliced onion for 5 minutes. Add mushrooms, season with salt and pepper, and cook for 10 minutes.

3. Mix 2 minced garlic cloves, season with thyme and nutmeg, then pour in bechamel and stock. Mix to combine.

4. Add the sauce into the string beans, stir to cover, and transfer into a baking pan. 

5. Top with torn-up ciabatta and bake for 20 minutes.

Tips for success: 

Here are a few tips for success and variations you can try to make this the best string bean casserole you've ever had.

• Substitute Campbell’s cream of mushroom soup if you can’t find bechamel sauce and don’t want to make your own white sauce. 
• Make it cheesy by adding shredded parmesan cheese.   
• To make this dish vegan, substitute the bechamel sauce and chicken stock with vegetable stock. It won’t be creamy but it will taste delicious.   

What can I top this casserole with? 

If you want to add some crunchy toppings to this dish, there are some great options. Try panko breadcrumbs, sliced almonds, French’s fried onion strings, chopped pecans, or walnuts.  

Can I make this string bean casserole in an instant pot?  

You can definitely make string bean casserole in a pressure cooker. This is a great option when you need to use the oven to make another dish or don’t want to heat up this large appliance. 

To start, use the saute function to cook the onions, mushrooms, garlic, thyme, and nutmeg. Off the heat add the bechamel sauce, stock, and green beans. Seal on the lid, set the time for 20 minutes, and allow to cook.

While the casserole cooks, toast the ciabatta in the oven until it’s lightly golden brown. When the timer goes off for the casserole, carefully release the pressure, remove the lid, top with the ciabatta bread, and serve. 

What other vegetables can I add to this dish?   

If you want to add extra vegetables to string bean casserole, there are lots of options to choose from. Try asparagus, broccoli, cauliflower, potatoes, butternut squash, zucchini, or eggplant. 

How to store:

Store any leftover casserole in an airtight container in the refrigerator for up to five days. Reheat it in the microwave with 30-second increments until it’s hot all the way through. 

To freeze the entire casserole, wrap it in aluminum foil and plastic wrap. Label it with what it is, how to cook, and the date. Labeling will help you remember later. Remember that if you cook it from frozen, it will take longer to cook in the oven without thawing first. Keep the foil on until the last 30 minutes of cooking so the top can brown.

FAQs: