2large Idaho all-purpose potatoes (about 3/4 pound), peeled and grated
Preheat the oven to 375°F. Lightly oil a shallow 2-quart baking dish or spray with nonstick cooking spray.
Heat a large skillet over medium high heat. Add the ground beef and cook, stirring frequently, until the beef is completely browned. Drain in a colander. Carefully wipe out the skillet, and return it to medium heat.
Heat 1 tablespoon of the the olive oil in the skillet over medium heat. Add the carrots, onions and garlic and sauté for 4 minutes, until tender. Add the scallions and the browned ground beef and stir to combine. Season with salt and pepper and stir in the oregano and chicken broth. Bring to a simmer then stir in the sour cream, and 1 cup of the shredded cheese. Simmer for 3 minutes, until the cheese is melted and everything is blended.
Turn the mixture into the prepared baking dish. Place the shredded potatoes in a clean dishtowel and twist and squeeze over the sink to remove as much water as possible from the potatoes. Shake the potatoes into a medium sized bowl. Toss the shredded potatoes with the remaining tablespoon of oil, and season with salt and pepper.
Evenly distribute the potatoes over the ground beef mixture. Bake for 40 to 50 minutes until the potatoes are tender and browned on top. Sprinkle the remaining cup of shredded cheese on top of the potatoes and return the casserole to the oven for 5 minutes, until the cheese has melted. Serve hot.