Vegetarian Shepherds Pies

Name: Vegetarian Shepherd's Pies
Ingredients: 1 pound Yukon Gold or white potatoes, peeled and cut into 1-inch chunks; ½ cup buttermilk; 1 tablespoon butter; ¾ teaspoon salt, divided; ½ teaspoon freshly ground pepper, divided; 1 tablespoon extra-virgin olive oil; 1 large onion, finely diced; ½ cup finely diced carrot; 1 tablespoon water; ¾ cup frozen corn kernels, thawed; 1 teaspoon chopped fresh thyme or 1/2 teaspoon dried; 3 tablespoons all-purpose flour; 1 14-ounce can vegetable broth; 1 1/2 cups cooked or canned (rinsed) lentils (see Tip)