Ingredients

4teaspoons olive oil, divided
1/2cup chopped onion
2carrots, chopped
2celery stalks, chopped
2cloves garlic, minced
1pound ground turkey breast
1teaspoon dried thyme
1teaspoon dried oregano
1/4teaspoon ground black pepper
128-ounce can crushed tomatoes
3large or 4 medium Yukon Gold potatoes (about 1 pound), peeled and cut into 2-inch pieces
1/4cup reduced-fat sour cream
2tablespoons nonfat milk
2scallions (green and white parts), chopped