Shepherds Pie

I've made this recipe a couple times and the family approved it as blog worthy. :)

-America's Test Kitchen, modified

1-1/2 pounds lean ground beef

Salt and pepper

2-1/2 pounds russet potatoes, peeled and cut into 1-inch chunks

2 tablespoons unsalted butter, melted

1/2 cup milk

1 large egg yolk

salt & pepper

8 scallions, green parts only, sliced thin (optional)

2 teaspoons vegetable oil

1 onion, chopped

4 ounces white mushrooms, trimmed and chopped (optional)

1 tablespoon tomato paste

2 garlic cloves, minced

2 tablespoons all-purpose flour

1-1/2 cups beef broth

2 teaspoons Worcestershire sauce

1 bay leaf

1 tsp. dried thyme

2 cup frozen peas & carrots

2 teaspoons cornstarch

Place potatoes and 1 tablespoon salt in large saucepan; add water to cover. Bring to boil, then reduce to simmer and cook until potatoes are tender, 8 to 10 minutes. Drain potatoes; return to saucepan over low heat, stirring constantly, to evaporate any remaining moisture, about 1 minute. Off heat, mash potatoes smooth with potato masher. Stir in butter. Whisk milk and egg yolk together in bowl, then stir into potatoes. Stir in scallions; season with salt and pepper to taste. Cover; set aside.

Heat oil in broiler-safe 10-inch skillet over medium heat until shimmering. Add onion and mushrooms and cook until vegetables begin to soften, 4 to 6 minutes. Add ground beef and season with salt and pepper. Cook until no longer pink. Stir in tomato paste and garlic and cook until bottom of skillet is dark brown, about 2 minutes. Sprinkle with the flour, stir and cook for 1 minute. Stir in broth, Worcestershire, bay leaf, thyme, and carrots; bring to boil, scraping up any browned bits.

Combine cornstarch and remaining 2 teaspoons water in bowl, then stir into skillet. Continue to simmer, stirring constantly, until filling is slightly thickened, about 30 seconds. Remove bay leaf. Season with pepper to taste.

Adjust oven rack 6 inches from broiler element and heat broiler. Place mashed potatoes in large zipper-lock bag; snip off corner to create 1-inch opening. Pipe potatoes evenly over filling to cover entire surface. Smooth potato with back of spoon, then use tines of fork to make ridges over surface. Place skillet on rimmed baking sheet; broil until potatoes are golden and sauce is bubbling, 10 to 15 minutes. Let cool slightly; serve.