1 teaspoon onion powder

1/2 teaspoon garlic power

1. Arrange a rack in the middle of the oven and heat to 400 F. Meanwhile, cook the potatoes.

2. Place the potatoes in a large (3- to 4-quart pot). Cover with about 2 quarts of water, stir in 1 teaspoon of the 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.

3. Heat the oil in a large oven-safe skillet -- 12-inch cast iron is best -- over medium-high until shimmering. Add the beef and 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.

4. Add the vegetables, water, flour, ketchup, onion powder and garlic powder. 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.

5. Drain the potatoes and return them to the now-empty pot. Add the milk, butter, and remaining 1 teaspoon salt, and mash to desired consistency (for shepherd's pie we like a pretty smooth mixture). Stir in the egg yolk.

6. Use a large spoon to dollop the mashed potatoes over the beef. Use the spoon to smooth the potatoes into an even layer.

7. 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.

Recipe notes: Refrigerate leftovers in an airtight container for up to three days. If you'd rather serve in a casserole dish or do not own an oven-safe skillet, transfer the filling mixture to a 3-quart casserole dish before topping with the potatoes.

(Meghan Splawn is associate food editor for TheKitchn.com, a nationally known blog for people who love food and home cooking. Submit any comments or questions to editorial@thekitchn.com.)