Bake the garlic Texas toast according to package directions until crispy and golden brown. If using the garlic Parmesan butter, brush it over the toast while still hot. Press the center of each slice in with the back of a spoon to create a shallow crater.
Heat a large griddle or skillet over medium-high heat and add the avocado oil. Cook the onions and peppers for 8-10 minutes until soft and caramelized, adding mushrooms if using. Stir in the garlic during the final minute, then remove the vegetables and set aside.
Increase the heat and lay the shaved steak down in one layer. Let it sit untouched for 3-4 minutes on the first side, then flip and chop into bite-sized pieces.
After another 2-3 minutes, season with the salt, pepper, garlic powder, and onion powder. Return the vegetables, add 1 tablespoon of Worcestershire sauce, and mix for a minute or two.
Add the provolone and white American and mix until the cheese fully melts through the steak and vegetables.
Spoon a tablespoon of queso into each toast crater, pile the cheesy steak mixture on top, and drizzle with blackened ranch. Finish with crispy fried onions, parsley, and cherry peppers, and serve immediately.