Clean the gills out of your portabella mushroom caps, and remove the stem.
In a medium bowl, combine the onion, tomatoes, garlic, panko, pork, ricotta, Porcini BBQ Genie spice, Worcestershire, olive oil and balsamic and mix until just combined. Don’t over handle it.
Fill each mushroom cap with the filling you just made.
Place them directly on the grill and close the lid. Cook until internal temp is around 160.
Pile on the cheese to the top of each stuffed mushroom and close the lid again. Cook just until cheese has melted.