Preheat your broiler to high. Place the jalapeños on a baking sheet and broil for 8–10 minutes, turning occasionally, until charred. Transfer them to a heatproof bowl, cover with plastic wrap, and let steam for 10 minutes.

Once cooled, peel off the skins, and remove the stems and seeds. In a blender, combine the peeled jalapeños with soaked cashews, water, rice vinegar, minced shallot, garlic powder, cucumber, lemon juice, salt and pepper. Blend until smooth.

Slice the portobello mushrooms into thick strips. In a bowl, mix olive oil, soy sauce, balsamic vinegar, and black pepper. Add mushroom strips and marinate for at least 15 minutes.

Preheat your grill or grill pan. Cook the marinated portobello mushrooms for 3–4 minutes per side until charred and tender. Remove from heat.

Warm the tortillas on a skillet over medium heat for about 30 seconds on each side. Keep warm in a towel.

Assemble the tacos by spreading grilled mushrooms on each tortilla, topping with avocado slices, shredded cabbage, and cilantro. Drizzle jalapeño sauce over the top.

Serve immediately with your favorite sides.