Preheat oven to 200 degrees F.
In a medium bowl, combine cheeses.
Heat 1 teaspoon vegetable oil in a large cast iron skillet over medium low heat.
Working one at a time, add 1 tortilla to the skillet and sprinkle with ⅓ cup cheese mixture in an even layer.
Top with ⅓ cup chicken on half of the tortilla; season with salt and pepper, to taste.
Cook until the cheeses have melted and the underside is golden brown, about 3-4 minutes; gently fold in half, pressing lightly.
Keep warm in oven up to 20 minutes.
Repeat with remaining vegetable oil and tortillas to make 6 quesadillas.
Serve warm with desired toppings.
