Preparation

• Heat the oil in a 12-inch skillet over medium heat until shimmering hot.
• Meanwhile, in a medium bowl, toss the shallots with 1 cup of the flour, separating the rings and coating them thoroughly. Working with a handful at a time, shake off the excess flour and fry, stirring occasionally with a slotted spoon, until golden, 1 to 2 minutes. Transfer to a paper-towel-lined plate and season lightly with salt. Discard the flour and frying oil and wipe out the skillet.
• Bring an 8-quart pot of salted water to a boil. Boil the haricots verts until crisp-tender, about 4 minutes. Drain in a colander and cool under cold running water; pat dry. Position a rack in the center of the oven and heat the oven to 400°F.
• Position a rack in the center of the oven and heat the oven to 400°F.
• Melt the butter in the skillet over medium heat. Add the mushrooms and a pinch of salt; cook, stirring often, until most of the liquid has evaporated and the mushrooms are beginning to brown, about 7 minutes. Add the sherry and cook, stirring, until almost evaporated, about 1 minute. Sprinkle the remaining 3 Tbs. flour over the mushrooms and toss to coat. Slowly whisk in the broth and cream. Simmer, stirring occasionally, until the sauce thickens, about 10 minutes. Remove from the heat and stir in the haricots verts, 1 tsp. salt, and 1/2 tsp. pepper. Season to taste with more salt and pepper.
• Transfer to a 9×13-inch baking dish and bake until bubbling around the edges, about 20 minutes. Gently stir the beans to redistribute the sauce, top with the shallots, and serve.