This simple shepherd's pie with a sweet potato topping is full of flavor from fresh herbs, Worcestershire sauce, and ground pepper. The lean ground beef supplies a rich meaty flavor, but lean ground turkey or a ground meat substitute would also work nicely.
– 2 pounds sweet potatoes, peeled and chopped (6 cups) – ½ cup reduced-fat sour cream – 2 tablespoons unsalted butter – ½ teaspoon salt, divided – 2 teaspoons cornstarch – 1 cup unsalted beef broth – 1 pound lean ground beef – 2 medium carrots, halved lengthwise and thinly sliced into half-moon
– 1 medium yellow onion, chopped – 3 medium cloves garlic, finely chopped – 2 tablespoons no-salt-added tomato paste – 1 tablespoon finely chopped fresh mixed tender and woody herbs (such as rosemary, sage and thyme) – 1 ½ cups frozen pea – 1 tablespoon Worcestershire sauce – ¾ teaspoon ground pepper
Preheat oven to 425°F. Place the sweet potatoes in a large saucepan with enough cold water to cover by an inch. Bring to a boil over high heat.
Reduce heat to medium, and cook, stirring occasionally, until tender when pierced with a fork, 10 to 12 minutes. Drain the sweet potatoes and return to the pan.
While heating with low heat for about 3 minutes, stir frequently until water has evaporated. Then, from the heat, beat using a potato masher until almost smooth. Stir in sour cream and butter with 1/4 teaspoon of salt. Reserve for a short time.
Whisk together cornstarch and broth in a small bowl. Heat a large oven-safe skillet over medium-high heat. Cook, breaking up the meat with a wooden spoon and stirring occasionally, until the beef is no longer pink, about 3 minutes after browning the underside of the ground beef, about 4 minutes.
Continue cooking, stirring constantly, until the carrots and onion are slightly softened, about 6 minutes. After adding the tomato paste and herbs, continue to stir constantly for 1 minute. Stir in the corn starch mixture, then add beef, peas, Worcestershire, pepper, and the remaining 1/4 teaspoon salt.
Cook until the mixture thickens, stirring frequently, about 2 to 3 minutes. Remove from the heat. Spread the mashed sweet potato mixture evenly over the beef mixture in the skillet. Spoon swirl the top to decorate. Bake for 15-20 minutes, or until the topping is heated through.