Wash and scrub the bellas. Pat dry. Brush olive oil all over and place with tops down on parchment lined baking sheet. Sprinkle a little salt, pepper and thyme on the bellas.
For stuffing: In a bowl, add chickpeas and mash well. Add all the ingredients till black pepper and mix well. Taste and adjust salt and seasoning.
NOTE: If you like your veggies well cooked, then saute the onions and carrots in oil, for 4-5 minutes on low-medium heat. Then add to chickpea mixture.
When ready to use the stuffing to stuff the portabellas (or to stuff bell peppers or tomatoes or squash) add the cashews, bread crumbs and oil and mix well. Add a few tsp broth or water if the mixture feels too crumbly.
Stuff the seasoned mushrooms with the stuffing. Top with tomato slices. Bake in preheated 350 degrees F for 30-40 minutes, or until the mushrooms are well done and the stuffing is golden. Or, they can be grilled on the BBQ for equally good taste!