Meat Loaf with Sour Cream-Mushroom Sauce

Name: Meat Loaf with Sour Cream-Mushroom Sauce
Cook time: 1 h 35 min
Total time: 1 h 35 min
Cuisine: American
Ingredients: ⅓ cup fat-free milk; 2 egg whites; 1 cup soft whole-grain bread crumbs (1 1/3 slices bread); ¼ cup chopped green onions; 2 teaspoons dried Italian seasoning, crushed; ¼ teaspoon salt; ⅛ teaspoon ground black pepper, plus more for garnish; 1 pound lean ground beef; Nonstick cooking spray; 1 tablespoon butter; 1 ½ cups sliced fresh mushrooms; 1 clove garlic, minced; ¼ cup thinly sliced green onions, plus more for garnish; 1 (8 ounce) container light sour cream; 2 tablespoons all-purpose flour; ¾ cup cold water; 2 teaspoons instant beef bouillon granules