Green Bean Casserole from Scratch
3 tablespoons canola oil, divided
1 medium onion, half diced and other half thinly sliced
8 ounces mushrooms, chopped
1 tablespoon onion powder
1 1/4 teaspoons salt, divided
1/2 teaspoon thyme
1/2 teaspoon freshly ground pepper
2/3 cup all-purpose flour, divided
1 cup low-fat milk
3 tablespoons dry sherry (a fortified wine)
1 pound fresh green beans (about 4 cups), cut in half
1/3 cup sour cream
1 teaspoon paprika
1/2 teaspoon garlic powder
1. Preheat oven to 400°F. Coat a 2 1/2-quart baking dish with cooking spray.
2. Cook green beans in boiling salted water until crisp and tender.
3. Heat 1 tablespoon oil in a large saucepan over medium heat. Add diced onion and cook until softened and translucent, about 4 minutes. Stir in mushrooms, onion powder, 1 teaspoon salt, thyme and pepper. Cook another 3 to 5 minutes. Sprinkle 1/3 cup flour over the vegetables; stir to coat. Add milk and sherry and bring to a simmer, stirring often to reduce flour lumps. Stir in green beans and return to a simmer. Cook, stirring, until heated through, about 1 minute. Stir in sour cream. Transfer to the prepared baking dish.
4. Whisk the remaining 1/3 cup flour, paprika, garlic powder and the remaining 1/4 teaspoon salt in a shallow dish. Add sliced onion; toss to coat. Heat the remaining 2 tablespoons oil in a large nonstick skillet over medium-high heat. Add the onion to oil and cook, turning once or twice, until golden and crispy, 4 to 5 minutes. Spread the onion topping over the casserole.
4. Bake the casserole until bubbling, about 15 minutes. Let cool for 5 minutes before serving.