Beef Mushroom Stew with Mashed Potatoes

Name: Beef & Mushroom Stew with Mashed Potatoes
Ingredients: 1 ½ pounds yellow potatoes, scrubbed and cut into 2-inch pieces; ½ cup low-fat milk; 2 tablespoons butter; ¾ teaspoon salt, divided; ½ teaspoon ground pepper, divided; 1 tablespoon extra-virgin olive oil; 1 pound lean ground beef; 8 ounces cremini mushrooms, quartered; 1 medium onion, diced; 4 cloves garlic, minced; 2 tablespoons all-purpose flour; 16 ounces stout (see Tip); 1 cup low-sodium beef broth; 1 tablespoon Worcestershire Sauce; 1 cup frozen peas and carrots