The Best Green Bean Casserole

Ingredients:

Casserole

• 30 g dried shiitake mushrooms
• 4 tablespoons unsalted butter
• 1 white onion, diced
• 340 g cremini mushrooms, thinly sliced
• 6 tablespoons flour
• 4 cups lightly salted chicken or vegetable broth
• 700 g green beans, ends removed and pods broken in half
• 3/4 cup heavy cream

Topping

• 1 white onion, halved and thinly sliced
• 1 cup of sour milk or kefir
• 2 cups of flour
• Vegetable oil, for deep-frying

Preparation:

1. Prepare the casserole:
   
   Place the dried shiitake mushrooms in a small bowl, pour in about 2 cups of boiling water, and cover with plastic wrap. Let steep for 20 minutes. Strain through a fine sieve, set aside 0.5 cups of the liquid, and chop the plump mushrooms.
2. In a large Dutch oven, melt the butter over medium heat. Add the diced onion and cook, stirring, until softened, 7 to 10 minutes. Add the cremini and shiitake mushrooms and cook until softened and most of the liquid has evaporated, 10 minutes. Sprinkle with flour and cook, stirring, for 1 minute. Add the broth and mushroom liquid. Bring to a boil, then reduce heat to medium-low and simmer until the liquid thickens, 5 to 10 minutes.
3. Bring a saucepan of salted water to a boil. Add the green beans and cook until crisp-tender, 7-10 minutes. Drain, shake off excess water, and transfer the beans to the mushroom sauce. Cook, stirring occasionally, until the beans are very tender and the sauce has thickened, 10-12 minutes. Stir in the heavy cream and season with 2 teaspoons of salt and black pepper.
4. Topping:
   
   Soak the chopped onion in the sour milk for 5 minutes. In a medium bowl, combine the flour and 1 teaspoon of salt. In a large saucepan, heat 2–3 inches of vegetable oil to 350°F (175°C) with a deep-fry thermometer. Drain the onion, toss it with the flour, and shake off any excess oil. Fry the onion until golden brown, 4–6 minutes. Transfer to paper towels to drain.
5. Preheat oven to 175°C.
   
   Transfer the green bean filling to a 4-quart baking dish and top with the fried onions. Bake for 30 minutes.
   
   Note
   
   The casserole and topping can be prepared 2 hours in advance and refrigerated. Bring to room temperature and reheat in the oven. Top with fried onions and bake for another 5 minutes.