Vegan Green Bean Casserole

1. Make onion topping: Preheat oven to broil and line a medium baking sheet with aluminum foil. In a
medium bowl, toss onion with olive oil and season with salt and pepper. Add flour and breadcrumbs and toss to coat onions. Broil, tossing every 2 to 3 minutes, until onions are crisp and golden, about 6 to 8 minutes in total. Turn oven to 375°.

2. Prepare an ice bath. To a large pot of boiling water, add green beans and cook until bright green, about 6 minutes.  With a slotted spoon or tongs, quickly transfer green beans to ice bath to cool, then drain and transfer to a large bowl.

3. In a large ovenproof skillet, heat 2 tablespoons olive oil over medium heat. Add shallots and cook, stirring
occasionally until tender, about 5 minutes. Add mushrooms and season with salt and pepper. Cook, stirring often, until mushrooms are golden, about 5 minutes more. Stir in garlic then transfer mixture to the bowl with the green beans.

4. Heat remaining 4 tablespoons of olive oil in the same skillet over medium heat. Whisk in flour and cook until
golden, about 2 minutes. Gradually whisk in milk and bring to a simmer. Be sure liquid doesn’t reach a full boil.
Cook until thickened, about 4 minutes. Remove from heat, season to taste with salt and pepper, then add green bean mixture and toss until even combined. Transfer mixture to a medium casserole dish.

5. Bake until warmed through and bubbling around the edges, about 20 minutes. Top with "fried" onions and bake 5 minutes more.