1 On large rim mend baking sheet, toss shallots with 1/3 cup of the flour. In a large, deep skillet, heat 1 inch of oil until shimmering. Add the shallots in two batches and fry over moderate heat until very crisp, about 3 minutes. Using a slotted spoon, transfer to paper towels, sprinkle with salt.2 In a large pot of boiling salted water, cook the beans until just tender, about 5 minutes. Drain and refresh under cold running water; pat dry3 Melt butter/margarine in a pan. Add the onion and cook over low heat, stirring occasionally, until softened, about 5 minutes. Add paprika, cayenne and large pinch of pepper; cook for 1 minute, stirring4 Add the mushrooms, cover and cook over moderate heat until softened, about 5 minutes. Uncover and cook, stirring, until browned, about 5 minutes longer. Stir in remaining 3 tablespoons of flour and gradually stir in the stock until smooth. 5 Simmer the mushroom sauce over low heat, until thickened, about 5 minutes.6 Add the beans. Covere and simmer, stirring occasionally, until beans are heated through, about 5 minutes. Season with salt and pepper. 7 Transfer to a baking dish. Cover the casserole with the foil and bake at 400 degrees until bubbly, about 20 minutes. Uncover, scatter shallots on top and serve.

And updated green bean casserole. Can also be done with cremini mushrooms.

Source:

Adapted from Food and Wine, November 2001