Line a plate with two paper towels. Place two small portobello mushroom caps on the paper towels, then cover with two more paper towels. Top with another plate.
2. Step
Meanwhile, in a small bowl, mix together mayonnaise, ketchup, worcestershire sauce, garlic salt, and hot chili sauce.
3. Step
Place a slice of Swiss cheese down on a counter top, then place a slice of American cheese on top, folding the corners of the American cheese in towards the center. Do the same with Swiss cheese, forming a ball shape.
4. Step
Place the cheese ball on one mushroom cap and then sandwich the other on top of it, pressing down to make the mushroom edges touch. Take a piece of clear plastic wrap and wrap it around the mushroom burger, twisting the sides like a piece of candy to release all of the air. Tuck the plastic wrap under the mushroom and refrigerate for 10-15 minutes.
5. Step
Put the egg, flour, and bread crumbs into 3 separate bowls.
6. Step
Remove plastic and coat mushroom burger in flour, egg, then bread crumbs. Dip in egg wash and bread crumbs one more time.
7. Step
Heat vegetable oil in a large pan until it is 375ºF (190ºC) and fry mushroom burger for 1-2 minutes or until golden brown.
8. Step
Remove burger onto paper towel to drain excess oil and let cool 1-2 minutes.
