Preheat the oven to 350 degrees. On a baking sheet lined with Tin Foil, arrange the Tortillas separately and top each with a half ounce of Cheddar. Bake just until Cheese is melted, about 3 minutes. Remove from oven. Meanwhile, heat the Cooking Oil in a large sauté pan over medium high heat until hot. Add the Beef and brown for 2 minutes. Add the Mushrooms and stir. Reduce heat to medium and continue to cook until Beef is no longer pink and Mushrooms have shrunk slightly and begun to caramelize, about 8 minutes. Top each Tostada with a quarter of the Meat mixture and top with another half ounce of Cheddar. Place in the oven until top Cheese is melted, about 4 minutes. Transfer to a platter and garnish with shaved Radish, Avocado. Serve with Hot Sauce if desired.