Preheat oven to 400°F.
Place hasselbacked potatoes in casserole dish and coat with olive oil, making sure to get between the layers. Bake for one hour.
While potatoes bake, prepare taco meat. In a skillet, brown the ground beef and drain the fat. Add water and taco seasoning and cook to package instructions.
Prepare cheese slices.
Remove potatoes from oven and alternate layers of cheese and ground beef, with additional cheese slices on top. Return to oven and bake an additional 20-25 minutes.
Serve with taco toppings such as:
Sour cream, guacamole, shredded lettuce, tomatoes, salsa, more cheese, cilantro, green onion.