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1
Preheat the oven to 400u00b0F.
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2
Spray an 8- or 9-inch-square casserole dish with nonstick cooking spray. Set aside.
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3
Bring a large pot of salted water to a boil.
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4
Cut the green beans into 1 1/2-inch pieces. Slice the mushrooms, finely chop the onion, and mince the garlic.
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5
Once the water is boiling, add the green beans. Blanch for 3 minutes, until beans are bright green. Drain the green beans into a colander and rinse with cold water.
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6
Set a large pot over medium-high heat and add the olive oil. Once oil is hot, add the onions and mushrooms to the pot. Saute for 6-7 minutes, until the mushrooms are browned and shrunken and the onions are soft. Add the garlic and thyme and cook for 30 seconds longer, until fragrant.
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7
Sprinkle the flour over the mushrooms and onions. Stir with a spatula to coat. Slowly pour the vegetable broth into the pot, whisking to dissolve the flour. Pour in the nut milk, and season with salt and black pepper.
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8
Cook the sauce, whisking constantly, until it begins to bubble and thicken. Reduce the heat to medium-low and allow the sauce to simmer for 5-7 minutes more, whisking occasionally, until it is reduced by about half.
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9
Add the green beans to the pot and stir to coat with the sauce. Pour the green bean mixture into the casserole dish.
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10
Bake the green bean casserole on the middle rack of oven for 15 minutes.
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11
Open the oven and sprinkle the french fried onions in an even layer over the top. Continue baking for 5-10 minutes, until the casserole is bubbling at the edges.
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12
Check to see that casserole is done. Remove from oven or add time as needed.
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13
Allow to rest for 10-15 minutes before serving.
