Vegan Green Bean Casserole

Prep

1. Preheat oven to 375°F.
2. Cook green beans in a large pot of boiling salted water until halfway tender and bright green, about 4 minutes. Remove from the pot and immerse in ice water. Drain and set aside.
3. Purchase store-bought crispy onions to reduce cooking time. For a more flavorful option, you can also make crispy onions yourself. Slice the onions into thin half-moons and toss them with olive oil, flour, salt, and panko. Spread them in an even layer on two large baking sheets and roast for 20 minutes until they’re golden brown and beginning to crisp up. Toss onions midway through and roast for another 15 minutes.
4. For the filling, heat the olive oil in a large skillet. Add the mushrooms and cook until soft, 8 to 10 minutes. Stir in the tamari, garlic, red pepper flakes, and thyme. Add a pinch of salt and pepper.
5. For the béchamel sauce, first, make the roux: melt 2 tbsp butter in a large saucepan over medium-low heat. Whisk in 3 tbsp flour and cook, whisking rapidly until the roux is golden brown and smells mildly nutty, about 3 minutes. Add cashewmilk, one cup at a time, whisking continuously until it simmers and thickens. Add the second cup, whisking at low to medium heat and cook until the béchamel sauce is slightly thick and bubbling, about 5 minutes. Remove from heat and whisk in the parmesan. Season with salt and pepper.
6. Arrange green beans and mushrooms in a 2-quart baking dish. Pour the sauce over the green beans and mushrooms (it may not look like enough, but it will get saucier as it bakes). Cover tightly with foil and bake until the sauce is bubbling, 25–30 minutes. Remove the foil and continue to bake 15–20 minutes longer. Top with fried onions and continue to bake until the onions are slightly darker and fragrant, about 3 minutes. Remove from the oven and let set for 10-15 minutes before serving.