Preheat grill to high. Place whole poblano peppers directly onto the grill; char on all sides. Remove from heat, place into a bowl, cover with plastic wrap and let rest and steam for 5 minutes. Remove the stems, skin and seeds. Place the roasted peppers, sour cream, ranch dressing mix and 2 cloves garlic into a blender. Process until smooth and set aside.
In a small bowl, combine the olive oil, cumin, chili powder, paprika, 3 cloves minced garlic, salt, pepper, lime juice and Tabasco sauce.
Place the asparagus, zucchini, mushrooms, bell peppers and green onions on a sheet tray and toss with the marinade to coat the veggies. Place them onto the preheated grill and cook for 5 to 10 minutes, turning along the way, until crisp-tender. The green onions and asparagus will finish cooking first.
Allow the veggies to cool, cut into 2" strips and season to taste with salt and pepper. Heat tortillas over warm grill. Build your tacos with poblano cream on the tortilla, a portion of veggies, more poblano cream and a sprinkle of fresh cilantro, if desired.