1 lb Yukon gold potatoes, peeled and cut into 2-inch pieces 1 clove garlic, whole, plus 1 teaspoon garlic, minced, divided 2/3 cup buttermilk 1 tablespoon chives, chopped Sea salt and ground black pepper, to taste 4 teaspoon olive oil, divided 1 lb lean ground turkey breast 1 yellow onion, finely chopped (1 cup) 3 medium carrots, halved lengthwise and cut into half moons (about 1 cup) 1 celery stalk, diced (about 1/3 cup) 1 teaspoon fresh rosemary leaves, finely chopped 1 cup low-sodium chicken broth 1 tablespoon tomato paste 1/2 cup frozen peas

1. Preheat oven to 375.
2. Bring potatoes and whole garlic clove to a boil in a pot of water set over high heat. Cook until potatoes are tender, about 15-20 minutes, then drain well. Mash potatoes and garlic with a potato masher, ricer or food mill until smooth. Add buttermilk and chives and season with salt and pepper. Set aside.
3. Meanwhile, heat 1 teaspoon oil in a large nonstick skillet over medium-high heat. Add turkey and cook, stirring often and breaking meat into small pieces with a wooden spoon. Cook until no pink remains, about 8 minutes. Drain and discard fat; set turkey aside.
4. Heat 2 teaspoons oil in skillet over same heat. Add onion, carrots, celery and rosemary and cook, stirring occasionally, until vegetables are soft, about 8 minutes. Add reserved turkey, broth and tomato paste and continue to cook until most of liquid is absorbed, about 5 minutes. Stir in peas, transfer mixture to a shallow baking dish and cover with mashed potatoes in an even layer. Run a fork over top of potatoes in a crosshatch pattern or swirl with a spatula or the back of a spoon. Brush top with remaining 1 teaspoon oil and bake in oven until filling bubbling and top is golden brown, about 30 minutes. Let stand 5 minutes before serving.