How can I preserve the crispiness of tortillas in a tortilla casserole?
Today I made a casserole based on tortillas (basically nachos but with more ingredients and in a casserole dish). Besides tortillas, I've added a mix of vegetables (tomatoes, chilli peppers, paprika and avocado) as well as minced meat which I roasted with onions and bread. I prepared a sauce consisting of sour cream and cheese and mixed everything, except for the tortillas, together.
I then laid out a tortilla layer, added a layer with my meat and vegetable mix and so on until my casserole dish was full. Everything went into the oven for a short time (15 minutes) and while it tasted delicious, the tortillas were a tad too soft so that I had to use a fork. I hoped to achieve a casserole where my "filling" was juicy and creamy while the tortillas were crisp in order to make a meal that can also be eaten just with your hands.
Is there a way to make my tortillas chip more crispy? I thought about preheating them thoroughly and for a long time to remove every last bit of liquid they have. Would this make any difference? Are there other ways to preserve their crispiness without altering my recipe too much?
For reference, they don't need to be as crispy as right out of the bag. The degree of crispiness should be high enough that I can conformably eat them with my hands without having to worry to drop stuff that's on a tortilla.