1. In a medium skillet, heat the oil over medium-high heat until hot. Add the onions, garlic and minced peppers and cook, stirring frequently, until the onions are softened, 6 to 8 minutes. Stir in the huitlacoche and heat until it begins to bubble, stirring frequently, then remove from heat and set aside.
2. Assemble the quesadillas: Heat a tortilla on the stovetop (this can be done directly on the stovetop or using a comal, or griddle pan). Add sliced cheese to one-half of the tortilla, and when it has melted, add a scoop of the huitlacoche mixture. Fold the tortilla over and hold in a warm place until all of the quesadillas have been assembled. Repeat with the remaining tortillas. Serve immediately.