Here's a dish of straightforward comfort, a crave-worthy combo of softened onions and leeks in a creamy sauce. Make the dish through step 2 up to a day ahead, and then reheat the next day in the baking dish.
1 tablespoon butter
1 tablespoon olive oil
6 cups vertically sliced onion (about 3 large)
4 cups thinly sliced leek (white and light green parts only)
1 tablespoon chopped fresh thyme
3/4 teaspoon kosher salt
1/2 cup dry white wine
2 cups 1% low-fat milk
6 tablespoons all-purpose flour
1/2 teaspoon freshly ground black pepper
1/4 teaspoon freshly grated nutmeg
1/3 cup whole-wheat panko (Japanese breadcrumbs)
How to Make It
Preheat oven to 450°.
Heat a large Dutch oven over medium-high heat. Add butter and oil; cook 1 minute or until butter is foamy. Add onion, leek, and thyme; cook 5 minutes, stirring frequently. Sprinkle with salt; cover, reduce heat to medium-low, and cook 15 minutes or until onions are translucent, stirring occasionally (do not allow onion to brown). Add wine; bring to a boil. Cook 5 minutes or until liquid almost evaporates. Combine milk and flour in a small bowl, stirring with a whisk. Add flour mixture, pepper, and nutmeg to pan; return to a boil. Simmer 5 minutes or until mixture thickens.
Spoon onion mixture into a 2-quart glass or ceramic baking dish coated with cooking spray. Top with panko. Coat panko with cooking spray. Bake at 450° for 10 minutes or until bubbly and top is golden brown. Let stand 5 minutes before serving.