• Preheat the oven to 350°F/ 180°C.

Cook vegetables:

• Blanch beans: Bring a large pot of water to a boil. In the meantime, trim and cut the green beans into 2,5 cm/1-inch pieces. Add salt to the water and then the beans. Blanch for 3-4 minutes until they lose their raw edge but are still firm. Drain and place them immediately in a bowl with ice water (Note 2).

  2 lbs green beans
• Prepare vegetables: Wipe the mushrooms clean with kitchen towels (Note 5) and halve them. If larger, quarter them. Chop the onions.

  9 oz small mushrooms + 1 small onion
• Cook: Heat the oil in a large non-stick pan, add onion and cook for about 2 minutes. Add mushrooms and cook until they turn golden, and all the released juices evaporate about 8-10 minutes. Set aside. Adjust the taste with salt and pepper.

  1 tablespoon olive oil

White sauce:

• Mix: Pour the milk into a saucepan and add the flour gradually while whisking all the time.

  1 cup milk + 2 tablespoons flour
• Cook while whisking continuously until the sauce thickens; it will happen fast. Season with salt, pepper, and soy sauce if used. Stir in 3 tablespoons of grated cheese. Add a splash of extra milk if the sauce seems too thick.

  fine sea salt + ground black pepper + 1-2 teaspoons soy sauce + 3 tablespoon from 5 tablespoons Parmesan

Casserole:

• Mix: Add vegetables to the sauce (or pour the sauce over the veggies) and mix well. Adjust the taste with salt and pepper. Lightly oil a suitable casserole dish and pour in the mixture.
• Top: Combine Panko and remaining grated cheese in a small bowl. Top the casserole with this mixture.

  5 tablespoons Panko breadcrumbs + remaining cheese (2 Tbsp)
• Bake in the preheated oven until the Panko is golden, about 35-40 minutes.