In a bowl, combine the shredded chicken, melting cheese, Street Taco seasoning, salt, and pepper. Mix well so the filling is evenly seasoned.
Preheat the Blackstone griddle to medium heat. Add a small amount of oil and char the tomatoes until softened and lightly blistered. On a cooler section of the griddle, toast the chiles de árbol for about 1 minute, just until fragrant—do not burn. In a molcajete, mash the garlic first, then the chiles, followed by the tomatoes, Knorr, salt, and cilantro. Mash until chunky and well combined.
Reduce the griddle heat to low–medium and warm the tortillas just until soft and pliable to prevent cracking.
Add 1–2 tablespoons of the chicken mixture to each tortilla and roll tightly into flautas.
Add oil to the griddle and place the flautas seam-side down. Cook over medium heat, turning gently, until golden and crispy on all sides.
Serve hot and top with lettuce, onion, sour cream, queso fresco, and salsa molcajete.