Cabbage Gratin

cabbage, shredded 1 cup carrot, shredded 2 green onions, chopped 2 Tbsp butter 1 cup milk 2 eggs 2 cups swiss cheese, shredded 1 tsp seasoning salt (or more to taste) 1/2 tsp pepper TOPPING 1/4 cup parmesan cheese 2 tablespoons fresh parsley, chopped