green bean casserole with crispy onions

Name: green bean casserole with crispy onions
Cuisine: American
Ingredients: Crispy Onions; 2 medium yellow onions, halved and thinly sliced; 1/4 cup all-purpose flour; 2 tablespoons panko or plain breadcrumbs; 1/2 teaspoon table salt; Freshly ground black pepper; Canola, safflower, peanut or other high-heat oil, for deep-frying; Mushroom Sauce; 3 tablespoons butter; 12 ounces mushrooms, thinly sliced or coarsely chopped; Few gratings fresh nutmeg (optional); Freshly ground black pepper; 3/4 teaspoon table salt; 2 garlic cloves, minced; 3 tablespoons all-purpose flour; 1 1/2 cups vegetable or chicken broth; 1/2 cup heavy cream