Fresh green beans, browned mushrooms and a homemade white sauce give this casserole a creamy center. Add the fried onions in two stages so the final layer stays crisp.
Recipe-development note: this version has not been kitchen-tested by Chefly. Cooking times and yield are estimates; use the doneness checks below.
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Ingredients
Estimated yield: 6–8 side servings. Equipment: a roughly 2-quart baking dish, saucepan and skillet.
- 1 1/2 pounds fresh green beans, trimmed
- 8 ounces mushrooms, thinly sliced
- 2 tablespoons unsalted butter
- 2 tablespoons all-purpose flour
- 1 cup low-sodium vegetable broth
- 1 cup whole milk
- 1 teaspoon soy sauce, optional
- 1/2 teaspoon fine salt, or less if the broth is salty
- Black pepper to taste
- 1 1/2 cups crisp fried onions, divided
Contains milk and wheat; soy sauce and packaged ingredients may add other allergens. Check labels.
How to make green bean casserole
- Heat the oven to 375°F (190°C). Blanch the beans in boiling water for about 4 minutes, until bright green and starting to soften. Drain and dry well.
- Melt the butter in a skillet over medium heat. Add mushrooms and cook until their released liquid has evaporated and they begin to brown. Stir in flour and cook for about 1 minute.
- Gradually whisk in broth and milk. Simmer gently, stirring, until the sauce coats a spoon. Add optional soy sauce and pepper. Taste before adding salt.
- Fold in the beans and transfer to the baking dish, leaving space below the rim. Scatter half the onions over the surface. Bake for approximately 20 minutes.
- Add the remaining onions and bake for about 5 minutes more, until the topping is golden and the center reaches 165°F (74°C). If the topping browns too soon, cover loosely with foil and continue heating. Let stand briefly before serving.
Texture and substitutions
A watery sauce usually needs better-drained beans or more evaporation from the mushrooms. Thicken the sauce before assembling rather than hoping the oven will remove excess liquid.
This method is written for fresh beans. Frozen beans can release extra water and have not been verified with these quantities. For the most predictable starting point, use fresh beans and the stated dish capacity.
Making ahead and storing leftovers
A chilled assembled casserole needs longer than the suggested baking time. Keep the onion topping separate until baking, follow the baking-dish manufacturer’s temperature-change guidance and check the center rather than relying on time alone.
Refrigerate perishables within 2 hours, or 1 hour above 90°F (32°C), in shallow containers at 40°F (4°C) or below. Use refrigerated leftovers within 3–4 days and reheat to 165°F (74°C). See USDA leftover guidance and the FoodSafety.gov temperature chart.
For another vegetable side, try crispy roast potatoes.