To make the pico de gallo: Combine the onion, tomatoes, cilantro, serranos, salt, pepper, and lime juice. Refrigerate until needed.
To make the chipotle cream sauce: Warm the béchamel and whisk in the chipotle concentrate. Hold warm for service.
To make the enchiladas: Heat the oil in a large sauté pan. Saute the onions and garlic for 1 minute, then add the mushrooms, zucchini, oregano, and coriander and stir until just hot through (2 to 3 minutes). Remove from the heat and add salt and pepper. Pour into a hotel pan and allow to cool to room temperature. Once cooled, stir in the green chiles and 12 oz. of the cheese.
Dip the tortillas in a hot fryer for 10-15 seconds to soften and set them aside on a sheet pan with a screen to drain. Top each tortilla with 2 ½ oz. mushroom filling and roll it up. Place the enchiladas seam-side down in two rows in an oiled 200 pan.
Pour the chipotle cream sauce over the enchiladas and cover tightly with foil. Bake in a 350-degree oven until the enchiladas reach an internal temperature of 165 degrees. Remove the foil and cook until the cheese is well melted. Garnish with the pico de gallo and cilantro. Serve 1 enchilada per portion.