1 1/3 pounds ground beef
1 tablespoon plain yogurt
2 teaspoons dried thyme
salt and pepper to taste
4 ounces feta cheese

6 tablespoons olive oil
1 large white onion, sliced into rings
1 1/3 cups uncooked green lentils
3/4 cup uncooked long-grain white rice
salt and pepper to taste
1/4 cup plain yogurt or sour cream (optional)