Easy Shepherd’s Pie

Name: Easy Shepherd’s Pie
Prep time: 25 min
Cook time: 45 min
Total time: 1 h 10 min
Cuisine: British, European
Ingredients: 3 pounds russet potatoes (4 to 5 large), peeled and diced; 2 teaspoons kosher salt, divided; 1/2 cup whole or 2% milk; 4 tablespoons unsalted butter; 1 large egg yolk; 1 teaspoon vegetable oil; 1 1/2 pounds lean ground beef; 1 teaspoon kosher salt; 1 (10-ounce) bag frozen vegetable medley, such as carrots, peas, green beans, and corn; 1/2 cup water; 2 tablespoons all-purpose flour; 2 tablespoons ketchup; 1 teaspoon onion powder; 1/2 teaspoon garlic power