Creamy Baby Portobello Green Bean Casserole
There’s something undeniably comforting about a classic green bean casserole — but this version takes it to a whole new level.
Imagine tender green beans enveloped in a silky cream sauce, studded with earthy baby portobello mushrooms, and topped with a golden crown of crispy fried onions. It’s a dish that feels both nostalgic and elevated, perfect for holiday tables, potlucks, or any gathering where you want to impress without the stress.
This casserole isn’t just creamy — it’s rich, savory, and layered with flavor. From the gentle bite of blanched green beans, to the umami depth of sautéed mushrooms, and the irresistible crunch of fried onions, every forkful delivers a satisfying contrast of textures. And with a make-ahead option built right in, it’s as practical as it is indulgent.
Whether you're hosting a crowd or simply craving a cozy side dish, this recipe promises to be a standout. It serves 12, but don’t be surprised if there are no leftovers — this is the kind of comfort food that disappears fast.
Ingredients:
- 1 tablespoon olive oil
- 8 ounces baby portabello mushrooms, cleaned and thinly sliced
- 2 pounds green beans, cleaned with stalk ends trimmed
- 3 tablespoons salted butter
- 3 tablespoons all-purpose flour
- 3 cups heavy cream
- ½ small white onion, diced
- 2 garlic cloves, minced
- 2 cups French’s® crispy fried onions
- Kosher salt and pepper, to taste
Method
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Step One:
Cook mushrooms and green beans
Heat oven to 350 F. Heat olive oil in a large skillet. Add mushrooms and stir to coat. Sprinkle with kosher salt and stir. Allow mushrooms to release their natural moisture, and cook until browned, about 5 minutes.
While mushrooms cook, blanch green beans. To do this, bring a large pot of heavily salted water to just simmering. Working in batches, place handfuls of green beans in the pot, and cook for 30 seconds. Using a large, slotted spoon, remove the beans to a large bowl of ice water to stop the cooking process. Repeat this process until all beans are blanched.
Remove from ice water, and place beans in a 9-by-13-inch casserole dish and set aside. Once mushrooms are browned, remove from pan and set aside.
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Step Two:
Make the sauce
Melt butter in the same pan over medium heat and whisk in the flour to create a roux. Cook for a few minutes, whisking constantly, until roux is golden brown.
Slowly whisk in heavy cream to create a smooth sauce. Stir in onion and garlic, and season with salt and pepper, to taste.
Cook sauce, stirring occasionally, for 5 minutes. Never bring the sauce to a boil, or it will curdle and separate.
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Step Three:
Bake and top
Stir mushrooms into sauce. Pour sauce over green beans and add 1 cup fried onions. Stir everything together until all beans are coated in sauce and in an even layer in the pan.
Bake in preheated oven for 30–35 minutes, or until beans are tender.
Top with remaining fried onions and cook for 5 additional minutes.
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Step Four:
Make-ahead instructions
If making ahead, prepare casserole through mixing the mushroom cream sauce with the beans. Allow to cool before covering the dish with plastic wrap. Refrigerate overnight. When ready to bake, remove the plastic wrap, add fried onions, and bake as directed.