Preheat a large cast-iron skillet over high, add corn; cook for 4 to 5 minutes, stirring occasionally, until lightly charred (some kernels may pop out of the skillet).
Remove corn from skillet; set corn aside.
Add oil to heated skillet let warm for 30 seconds on high. Add mushrooms, oregano, ancho chile powder, and cumin. Cook, stirring often for 2 to 3 minutes or until mushrooms begin to brown.
Stir in garlic and salt, reduce heat to medium. Cook, stirring occasionally for 2 to 3 minutes or until mushrooms are tender but still somewhat firm.
Remove mixture from heat and stir in charred corn.
Place a generous ½ cup (120ml) mushroom mixture in each Casa Mendosa® 100% Corn Small Tortilla.
Top each with 2 tbsp. (30ml) onion, 2 tbsp. (30ml) salsa, a few serrano and red Fresno Chile slices.