Preparation

• Position a rack in the center of the oven and heat the oven to 200°F.
• Heat the oil in a 10-inch skillet over medium-high heat. Add the mushrooms and onion and cook, stirring occasionally, until beginning to brown, 5 to 6 minutes. Add the ham, and red and green peppers, and continue to cook, stirring occasionally, until browned, 2 to 3 minutes. Remove from the heat.
• Heat a 12-inch cast-iron skillet over medium-low heat. Mix the cheeses together and divide into four portions. Divide the ham mixture into four portions. Lightly oil the skillet. Place a tortilla in the skillet and sprinkle one half with one portion each of the cheese and ham mixtures. Fold the other half of the tortilla over the filling, gently pressing down with a spatula. Cook, flipping once, until golden brown on both sides, 4 to 5 minutes total. Keep warm in the oven. Repeat with the remaining tortillas and filling, oiling the skillet between each quesadilla. Serve with the sour cream.