Slice portobello caps into 1/2 inch filets. In a bowl, whisk together olive oil, chili powder, cumin, paprika, oregano, garlic powder, lime juice, and Worcestershire sauce. Place portobellos in a large resealable bag and pour in marinade. Toss thoroughly to coat each filet. Set aside for 10 minutes while you prepare the rest of the dinner, or up to 24 hours in the fridge.
Preheat oven to 450 degrees. Set poblano and jalapeno on a baking sheet, then roast 15-18 minutes, turning once or twice, until charred all over. Set into a resealable bag to "sweat" for at least 5 minutes.
Break off the caps of the poblano and jalapeno, peel the skin off, and scrape out the seeds. Place into the bowl of a food processor or high speed blender along with the garlic cloves, parsley, cilantro, basil, cumin, lime juice, and oil. Blend until smooth, but not pureed. Visible flecks of herbs are more than okay! Pour into an airtight container or bowl and set aside.
Heat a couple tablespoons of avocado or olive oil over medium heat. Stir fry the red onion and peppers for 3-5 minutes until slightly charred. Place onto a clean plate and set aside. To the same skillet, dump in portobello slices and arrange with as little overlap as possible. Cook undisturbed for 3 minutes, then turn each piece over. Cut butter into 3-4 smaller pieces and scatter over the mushrooms in the pan. Cook another 2-3 minutes per side until butter melts and caramelizes around the mushrooms. Remove from heat to a clean plate.
To create a fancy pants board, arrange portobello slices in the center like you might a big cut of steak. Place piles of fajita vegetables evenly around the corners, and the bowl of chimichurri on one corner. Serve with a plate of tortillas and fresh pineapple chunks.