Clean large Portobello Mushroom removing dirt. If water is used to clean then pat both sides dry with towel. Remove the stem.
Heat olive oil, extra virgin in a small skillet to medium high heat.
Season Portobello Mushroom with sea salt and Adobo Seasoning on both sides, then place mushroom bottom side (where stem was). Cook for 4 to 5 minutes before turning over, watching closely to make sure it doesn't burn. Make adjustments to temperature as necessary. Turn mushroom over and place pepper jack slice on top and cook another 3 to 4 minutes.
Peel one avocado into a bowl and mash with a fork. Season with Topatio sauce, fresh minced or grated garlic, sea salt, Tajin with lime.
Spread bun with the guacamole made with avocado, then place the Portobello Mushroom with melted pepper jack on bun!