Savory Green Bean & Mushroom Gratin

1. Make the topping

Preheat your oven to 375°F. Pulse the white sandwich bread, 2 tablespoons of unsalted butter, 0.25 teaspoons of table salt, and 0.125 teaspoons of ground black pepper in a food processor until you have coarse crumbs. Transfer the crumbs to a large bowl and toss them with the canned fried onions. Set the mixture aside.

2. Cook the green beans

Bring 4 quarts of water to a boil in a large pot, adding 2 tablespoons of table salt once it reaches a rolling boil. Add the fresh green beans and cook for 4 to 5 minutes until they are crisp-tender. Immediately drain the beans and plunge them into a bowl of ice water to stop the cooking process. Spread the beans on a paper towel-lined baking sheet to drain completely.

3. Prepare the porcini mushrooms

Place the dried porcini mushrooms in a microwave-safe bowl with 0.5 cups of hot tap water. Cover the bowl with plastic wrap, cut a few steam vents, and microwave for 30 seconds. Let the mushrooms stand for about 5 minutes until they soften. Lift the mushrooms from the liquid, mince them, and strain the soaking liquid through a paper towel-lined sieve, reserving the liquid.

4. Cook the mushroom mixture

In a large skillet, melt the remaining 6 tablespoons of unsalted butter over medium-high heat until the foaming subsides. Add the minced medium onion, minced garlic cloves, sliced white button mushrooms, and sliced cremini mushrooms. Cook for about 2 minutes until the mushrooms start to release their moisture. Stir in the minced porcini mushrooms, the reserved soaking liquid, minced fresh thyme leaves, 1 teaspoon of table salt, and 0.25 teaspoons of ground black pepper. Continue to cook until the mushrooms are tender and the liquid has reduced, about 5 minutes. Sprinkle the all-purpose flour over the mixture and cook for another minute, stirring constantly.

5. Make the sauce

Reduce the heat to low and stir in the low-sodium chicken broth, followed by the heavy cream. Simmer the mixture for about 15 minutes until it thickens and bubbles gently, creating a dense, flavorful sauce that will coat the green beans perfectly.

6. Assemble and bake the gratin

Arrange the drained green beans in a 3-quart gratin dish. Pour the mushroom mixture over the beans and mix gently to coat them evenly. Sprinkle the prepared bread crumb and fried onion topping over the dish. Place the dish in the oven and bake for about 15 minutes until the top is golden brown and the sauce is bubbling.

7. Serve

Allow the gratin to stand for 5 minutes before serving, which helps the flavors meld and makes it easier to serve.