These are always a big hit with Mrs J and are one of my favorite things. I kept the sausage separate from the beans but there is no reason not to mix them up in the pan. The beans will take an hour or two, keep adding liquid as needed and mash the beans up some. I used the back of a wooden spoon, a potato masher will work fine as well.
I fired the oven with a baking stone on a rack in the oven center, ran the temp up to just shy of molten lead. Use a peel and deposit the tortilla with the beans and sausage onto the stone and give it just long enough for the cheeses to melt a bit and for the edges to just start browning. Any more and the tortilla becomes too brittle to fold. I used tongs to grab the edge and drag it back onto the peel. Slide it onto a plate and garnish with your favorite sauces and condiments.