Start by heating up two tablespoons of the vegetable oil in a large skillet over medium-low heat. Once it starts to sizzle, add the sliced poblanos, chopped mushrooms, and onion, and cook, stirring occasionally, until the onion starts to become translucent, about 6 to 8 minutes. Stir in the garlic and spices and cook for an additional 2 minutes, taste the filling for salt, then adjust and remove from the heat.
Heat the tortillas in the microwave for 30 to 45 seconds. You want them to be warm so they are easier to roll. A cold tortilla will rip.
Heat 1⁄2 inch (1.25 cm) of vegetable oil in a large skillet over medium-low heat. Once it starts to sizzle, working in batches of 5 to 6, take a tortilla and add about 1 tablespoon of the sautéed poblano and onions, then add two strips of the panela cheese. Roll tightly, then place in the skillet seam side down and fry for 2 to 3 minutes on each side until golden brown. Repeat with the remainder of the tortillas.
Arrange the flautas on a platter, then top with lettuce, onion, radish, and serrano. Crumble queso fresco over the flautas and finish with a drizzling of crema Mexicana and avocado salsa.