Ingredients
4 sweet potatoes, peeled and cut into 1-inch pieces (6 cups)
3 tablespoons extra-virgin olive oil
Coarse salt and freshly ground pepper
1 1/2 pounds ground beef (90 percent lean)
8 ounces cremini mushrooms, sliced (3 cups)
1 large onion, chopped (2 cups)
1/2 cup Pilsner-style beer
2 teaspoons cornstarch
2 teaspoons Dijon mustard
1 1/4 cups low-sodium chicken broth
Preparation
Preheat oven to 425 degrees. Cover potatoes with 2 inches water in a pot; bring to a simmer. Cook until tender, about 17 minutes. Drain and return to pot. Mash with 2 tablespoons oil; season with salt.
Place beef in a 10-inch cast-iron skillet over medium-high and cook, stirring occasionally and breaking up large pieces with a spoon, until browned, about 11 minutes. Transfer to a plate using a slotted spoon; pour off excess fat in skillet.
Add 1 tablespoon oil, mushrooms, and onion to skillet; cook, stirring occasionally, until browned, about 6 minutes. Add beer; cook until reduced, about 3 minutes. Whisk together cornstarch, mustard, and broth in a bowl; add to skillet and bring to a boil. Return beef to skillet; season with salt and pepper. Top with mashed potatoes. Bake until bubbling, 25 to 30 minutes. Serve hot.
