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1
Onions:
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2
Slice onion in half; place the flat half down on your cutting board and slice each half into thin rounds.
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3
Place in a baking dish and cover with buttermilk and soak for at least an hour.
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4
Combine dry ingredients and set aside.
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5
Heat oil in small fryer or large dutch oven to 375 degrees.
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6
Grab a handful of onions, throw into the flour mixture, tap to shake off excess, and plunge into hot oil. Fry for a few minutes and remove as soon as golden brown.
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7
Repeat until onions are gone.
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8
Casserole:
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9
Preheat oven to 350u00b0F. Bring a large pot of salted water to a boil. Add beans and cook until deep green and tender, about 10-15 minutes. Drain and rinse with cool water.
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10
In a large Dutch oven or heavy pot, melt 2 tbsp of butter on medium-high heat. Add the mushrooms and saute until they start sweating liquid, about 4 minutes. Add the onion, garlic, and a pinch of salt. Continue cooking, stirring often, until softened, about 6 minutes. Add the wine and simmer until it evaporates, about 3 minutes. Remove the mushroom mixture to a separate bowl.
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11
Combine the milk, cream, and chicken stock and bring to a simmer in a saucepan.
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12
Melt the remaining 4 tbsp butter in the Dutch oven over medium-low heat. Add the flour and whisk until creamy; about 2 minutes.
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13
Add the hot milk mixture and continue cooking, whisking frequently, until thickened, about 15 minutes. Whisk in Worcestershire sauce, mustard powder, and a generous amount of salt and pepper.
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14
Stir the mushroom mixture into the cream sauce and simmer, whisking frequently, for about 5 minutes for the flavors to marry. Taste and adjust the salt and pepper.
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15
Stir the green beans into the mushroom sauce and toss to combine. Pour the green bean mixture into a large, buttered casserole dish (about 2 quarts). Bake uncovered for 15 minutes. Add the grated cheddar and crispy onion strings and bake uncovered until cheese is melted; about 15 minutes.
