Old-School Green Bean Casserole

Featured in: Family Comfort Plates

This comforting green bean dish blends tender green beans with a savory mushroom sauce, enriched with butter, cream, and milk. The casserole is topped with crunchy fried onions, baked until bubbling and golden, delivering nostalgic flavors ideal for holiday feasts or family dinners. Simple steps include blanching beans, cooking mushrooms and onions in a creamy sauce, and layering with crispy onions for a delightful texture contrast.

Updated on Tue, 11 Nov 2025 11:02:00 GMT
A bubbling, creamy Old-School Green Bean Casserole topped with crispy, golden fried onions. Pin it
A bubbling, creamy Old-School Green Bean Casserole topped with crispy, golden fried onions. | weeknightwhisk.com

A nostalgic, creamy side dish featuring tender green beans, savory mushrooms, and crispy fried onions—a classic for holiday feasts and family dinners.

I grew up looking forward to my grandmother's green bean casserole every Thanksgiving. This version brings back all those family memories with just a bit of modern freshness.

Ingredients

  • Fresh green beans: 900 g (2 lb), trimmed and cut into 5 cm (2-inch) pieces (or use 900 g frozen cut green beans, thawed and drained)
  • Unsalted butter: 2 tbsp
  • Cremini or button mushrooms: 250 g (9 oz), sliced
  • Yellow onion: 1 small, finely chopped
  • Garlic cloves: 2, minced
  • All-purpose flour: 2 tbsp
  • Whole milk: 240 ml (1 cup)
  • Heavy cream: 120 ml (1/2 cup)
  • Low-sodium vegetable broth: 120 ml (1/2 cup)
  • Salt: 1 tsp
  • Black pepper: 1/2 tsp
  • Ground nutmeg (optional): 1/2 tsp
  • Crispy fried onions: 150 g (1 1/2 cups), store-bought or homemade

Instructions

Prep Oven & Beans:
Preheat oven to 180°C (350°F). Bring a large pot of salted water to a boil. Add green beans and cook for 5 minutes until just tender but still bright green. Drain and rinse under cold water. Set aside.
Make Mushroom Sauce:
In a large skillet over medium heat, melt butter. Add mushrooms and cook for 5-6 minutes until tender and browned. Add onion and garlic, cook for another 2-3 minutes until softened.
Thicken Sauce:
Stir in flour and cook for 1 minute, stirring constantly. Gradually whisk in milk, cream, and broth. Bring to a simmer and cook until thickened, about 5 minutes. Season with salt, pepper, and nutmeg.
Combine Beans & Sauce:
Add drained green beans to skillet and toss to coat evenly in sauce.
Assemble:
Transfer mixture to a 2-liter (2-quart) baking dish. Sprinkle half of crispy fried onions on top.
Bake & Finish:
Bake for 25 minutes until bubbling. Remove from oven, top with remaining onions, and bake for 5-7 minutes until golden and crisp. Let cool for 5 minutes before serving.
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Preparing this together last year with my niece turned into an unexpected cooking lesson and lots of laughter. She now insists it's the must-have side at every family dinner.

Make Ahead Tips

Assemble the casserole up to step 6 and refrigerate for up to 24 hours. Add onions and bake before serving.

Flavor Boosts

Add 50 g grated sharp cheddar or Gruy&re cheese to the sauce for a richer taste. The casserole pairs wonderfully with roast turkey or chicken.

Serving Suggestions

Serve straight from the oven as part of your holiday spread or alongside weekday meals as a cozy vegetarian side dish.

This classic, homemade Old-School Green Bean Casserole features tender green beans in a rich mushroom sauce. Pin it
This classic, homemade Old-School Green Bean Casserole features tender green beans in a rich mushroom sauce. | weeknightwhisk.com

This old-school casserole truly shines at gatherings—expect hearty helpings and happy memories around the table!

Common Questions

What is the best way to prepare the green beans?

Trim and cut fresh green beans into pieces, then blanch in boiling salted water for 5 minutes until tender but still crisp. Immediately rinse under cold water to stop cooking.

Can frozen green beans be used instead of fresh?

Yes, frozen cut green beans can be thawed and drained before cooking to maintain texture and flavor.

How do I achieve a creamy sauce for the dish?

Sauté mushrooms and onions in butter, then whisk in flour to create a roux. Gradually add milk, cream, and vegetable broth, simmering until thickened and smooth.

What gives the topping its signature crunch?

Crispy fried onions, either store-bought or homemade, are sprinkled on top and baked until golden and crisp, adding texture contrast to the creamy base.

Can this side dish be prepared in advance?

You can assemble the dish up to the baking step and refrigerate for up to 24 hours. Add the crispy onions and bake just before serving.

Old-School Green Bean Casserole

Creamy green beans with mushrooms and crispy fried onions, perfect for holiday or family gatherings.

Prep Time
15 min
Cook Time
35 min
Time Needed
50 min
Created by Ella Thompson


Skill Level Easy

Cuisine American

Makes 6 Portions

Dietary Info Meat-Free

What You'll Need

Vegetables

01 2 lb fresh green beans, trimmed and cut into 2-inch pieces (or frozen, thawed and drained)

Sauce Base

01 2 tbsp unsalted butter
02 9 oz cremini or button mushrooms, sliced
03 1 small yellow onion, finely chopped
04 2 garlic cloves, minced
05 2 tbsp all-purpose flour
06 1 cup whole milk
07 ½ cup heavy cream
08 ½ cup low-sodium vegetable broth
09 1 tsp salt
10 ½ tsp black pepper
11 ½ tsp ground nutmeg (optional)

Topping

01 1½ cups crispy fried onions (store-bought or homemade)

Step-by-Step

Step 01

Preheat oven: Set the oven temperature to 350°F.

Step 02

Blanch green beans: Bring a large pot of salted water to a boil. Add green beans and cook for 5 minutes until just tender and bright green. Drain and rinse immediately under cold water to halt cooking. Set aside.

Step 03

Cook mushrooms and aromatics: In a large skillet over medium heat, melt the butter. Add mushrooms and sauté for 5 to 6 minutes until browned and tender. Add onion and garlic; cook an additional 2 to 3 minutes until softened.

Step 04

Prepare sauce: Sprinkle flour over the vegetables and cook for 1 minute, stirring constantly. Gradually whisk in the milk, heavy cream, and vegetable broth. Simmer for 5 minutes until thickened. Season with salt, black pepper, and nutmeg if using.

Step 05

Combine green beans with sauce: Add the drained green beans to the skillet, tossing to coat evenly in the creamy sauce.

Step 06

Assemble casserole: Transfer the mixture to a 2-quart baking dish. Sprinkle half of the fried onions evenly on top.

Step 07

Bake first stage: Bake uncovered for 25 minutes until bubbling and heated through.

Step 08

Add topping and finish baking: Remove from oven, top with remaining fried onions, and bake for 5 to 7 more minutes until golden and crispy.

Step 09

Rest before serving: Allow to cool for 5 minutes before serving to let flavors meld.

Tools Required

  • Large pot
  • Colander
  • Large skillet
  • Whisk
  • 2-quart baking dish
  • Oven

Allergy Notice

Go through every ingredient to identify allergens and talk to your healthcare provider if you have concerns.
  • Contains milk (dairy) and wheat (gluten).
  • May contain soy if using store-bought fried onions.

Nutrition Information (per portion)

Nutrition details are for general reference and shouldn't replace advice from your doctor.
  • Caloric Content: 265
  • Fats: 15 g
  • Carbohydrates: 25 g
  • Proteins: 6 g