Clean Portobello mushroom cups by removing the stems and place in a shallow dish container.
Whisk together in a separate bowl, the balsamic vinegar, olive oil, shredded basil leaves, garlic, oregano, salt and pepper. Pour over the mushrooms and let it marinate at room temperature for 15 or 20 minutes.
Preheat the barbecue at medium high heat, place the mushroom on the grill reserving the balsamic marination for basting.
Grill the Portobello for 5 minutes on each side by consistently basting with a brush with the marination.
Top the mushroom with provolone cheese slices and let it melt for 2 minutes.
Remove the melted Portobello provolone burger from the grill and set aside.
Drizzle the burger buns with remaining Balsamic marination and warm on the grill for two minutes on each side in order to obtain a nice season toasty bun.
In a small bowl, combine the mayonnaise and sambal together and set aside.
Serve the mushroom burger on the toasted bun, dress with sliced tomatoes, lettuce and the spicy mayo.