Green Bean Casserole with Homemade Mushroom Sauce

Ingredients

For the recipe

• 800 g fresh green beans, weighed after trimming, cut into 4–5 cm / 1 1/2–2 inch pieces
• 300 g white or cremini mushrooms, cleaned and sliced
• 150 g onion, peeled and finely diced
• 12 g garlic, about 4 cloves, minced
• 60 g unsalted butter, divided: 5 g for the baking dish and 55 g for the sauce
• 40 g all-purpose flour
• 500 ml 2% milk, approximately 515 g
• 250 ml prepared low-sodium vegetable broth, approximately 250 g
• 10 g soy sauce, about 2 teaspoons
• 1 teaspoon dried thyme (1 g)
• 4 g fine salt, about 2/3 teaspoon, for the sauce
• 1/2 teaspoon ground black pepper (1 g)
• A small pinch of ground nutmeg (0.25 g)
• 120 g ready-made crispy fried onions, divided: 40 g for the filling and 80 g for the topping

Instructions

1. Heat the oven to 190°C / 375°F conventional, or 170°C fan. Grease a 23 x 33 cm / 9 x 13 inch baking dish with the measured 5 g butter. Bring a large pot of unsalted water to a boil and prepare a bowl of ice water.
2. Add the trimmed green beans to the boiling water and cook for 4–5 minutes, until bright green and crisp-tender. Transfer to the ice water to stop cooking, then drain very thoroughly and pat dry so they do not dilute the sauce.
3. Melt the remaining 55 g butter in a large deep skillet over medium-high heat. Add the mushrooms and cook for 6–8 minutes, stirring occasionally, until their released liquid mostly evaporates and some edges turn golden.
4. Add the diced onion and cook for 4–5 minutes until softened. Stir in the garlic and dried thyme for 30 seconds.
5. Sprinkle the flour evenly over the vegetables. Stir for 1–2 minutes, until no dry flour remains and the mushrooms are coated. Reduce the heat to medium so the flour does not scorch.
6. Gradually whisk in the milk, starting with a small splash to make a smooth paste around the mushrooms. Add the remaining milk in stages, then stir in the broth, soy sauce, salt, pepper and nutmeg.
7. Bring to a gentle simmer and cook for 4–6 minutes, stirring across the base, until the sauce lightly coats the back of a spoon. It should be creamy and pourable rather than stiff.
8. Take the skillet off the heat. Fold in the well-drained beans and 40 g of the crispy onions. Transfer to the prepared baking dish and spread evenly.
9. Bake uncovered for about 20–25 minutes, until the sauce is bubbling around the edges and the center is thoroughly hot. Check the center with a thermometer and continue if needed; the finished casserole should reach at least 74°C / 165°F.
10. Scatter the remaining 80 g crispy onions over the surface. Bake for another 5–8 minutes, just until the topping is golden and crisp. Watch closely and loosely shield with foil if it darkens too fast.
11. Let the casserole rest for 5 minutes before dividing into eight side-dish portions. Include an even share of the sauce and onion topping in each portion.