In a blender, combine chipotle peppers in adobo sauce, vegetable broth, fresh lime juice, granulated garlic, chili powder, cumin, and fine sea salt. Blend until smooth and well-combined. Set sauce aside.

Heat 1-2 tablespoons of avocado oil in a large skillet over high heat. Add sliced portobello mushrooms in a single layer and sear for 2-3 minutes without stirring. Stir and cook for another 2-3 minutes until tender and caramelized. Season with salt and pepper before removing from skillet.

In the same skillet, add another tablespoon of oil if needed, then add sliced bell peppers and red onion. Sauté over medium-high heat for about 6-8 minutes until tender and slightly charred, seasoning with salt and pepper to taste.

Return the sautéed mushrooms to the skillet with the peppers and onions. Pour the prepared fajita sauce over the mixture and stir gently to combine. Heat for 1-2 minutes.

Warm corn tortillas in a dry skillet for about 30 seconds on each side. Spoon generous portions of the fajita mixture onto each tortilla and add toppings like vegan sour cream, cilantro, and lime wedges.