Prepare the Green Beans
Bring a large pot of salted water to a boil.
Add the green beans and blanch for 3 minutes. Transfer them immediately to an ice bath to stop the cooking process and retain their vibrant color. Drain and set aside.
Create the Creamy Mushroom Base
Heat olive oil in a large skillet over medium heat.
Sauté the onions and garlic until fragrant, about 2 minutes.
Add the mushrooms and cook until tender, stirring frequently, about 5 minutes.
Sprinkle the whole wheat flour over the mixture and stir until fully incorporated.
Make the Sauce
Gradually whisk in the almond milk and broth. Simmer the mixture, stirring constantly, until it thickens, about 4-5 minutes.
Remove from heat and stir in the Greek yogurt, salt, black pepper, and paprika.
Assemble the Casserole
Preheat the oven to 375°F (190°C).
In a 9x13-inch baking dish, combine the green beans with the mushroom sauce. Mix until the beans are evenly coated.
Add the Topping
In a small bowl, mix the breadcrumbs, Parmesan cheese, and a drizzle of olive oil.
Sprinkle this mixture evenly over the casserole. Add fried onions on top if desired for extra crunch.
Bake and Serve
Bake in the preheated oven for 20-25 minutes, or until the top is golden brown and crispy.
Serve hot and enjoy!