Ingredients

For the potato layer:

• 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

For the filling:

• 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

1. Arrange a rack in the middle of the oven and heat to 400°F.
2. Depiction of the instructions in Instructions step 1
3. Place 3 pounds peeled and diced russet potatoes in a large (3- to 4-quart) pot. Cover with about 2 quarts of water, stir in 1 teaspoon of the kosher salt, and bring to a boil over high heat. Reduce the heat to medium-low, cover, and simmer until the potatoes are tender, 15 to 18 minutes. Meanwhile, make the filling.
4. Depiction of the instructions in Instructions step 2
5. Heat the oil in a large oven-safe skillet — 12-inch cast iron is best — over medium-high heat until shimmering. Add 1 1/2 pounds lean ground beef and kosher salt, breaking it into large chunks as you add it to the pan. Let the meat brown for 1 to 2 minutes undisturbed, then use a spatula to break up the chunks into smaller pieces. Cook, stirring occasionally, until browned, about 10 minutes total.
6. Depiction of the instructions in Instructions step 3
7. Add 1 (10-ounce) bag of frozen vegetables, 1/2 cup water, 2 tablespoons all-purpose flour, 2 tablespoons ketchup, 1 teaspoon onion powder, and 1/2 teaspoon garlic power. Cook, stirring occasionally, until simmering, 2 to 3 minutes. Remove from the heat. Don’t worry too much if the browned beef mixture looks a little soupy -- it will thicken in the oven.
8. Depiction of the instructions in Instructions step 4
9. Drain the potatoes and return them to the now-empty pot. Add 1/2 cup milk, 4 tablespoons unsalted butter, and remaining 1 teaspoon kosher salt and mash to desired consistency (for shepherd’s pie we like a pretty smooth mixture). Stir in 1 egg yolk.
10. Depiction of the instructions in Instructions step 5
11. Use a large spoon to dollop the mashed potatoes over the beef. Use the spoon to smooth the potatoes into an even layer.
12. Depiction of the instructions in Instructions step 6
13. Bake until the potatoes just begin to brown and the filling is bubbling, 25 to 30 minutes. Cool for 10 minutes to let the sauce thicken slightly before serving.
14. Depiction of the instructions in Instructions step 7