I have posted a recipe already for a veggie option of this, but it is such a good use of leftovers, and delicious, to boot, so I hope you'll forgive me a little variation. Home-made re-fried beans are so much better than the vile tasting (and smelling) gloop in tins. Just drain and rinse a tin of kidney, pinto or black beans and 'smush' for want of a better expression in a bowl with a potato masher until crushed and almost a puree, with bits of whole bean here and there for texture. Saute an onion and some garlic in a little oil, add a teaspoon of ground cumin, dried oregano and hot chilli powder and cook a while longer. Now stir in the beans and three skinned, chopped tomatoes (I added some chopped pepper too), and cook and stir for 5 minutes or so until amalgamated and thick. Season with salt to taste. Spread on wheat tortillas and layer with shredded cooked chicken and grated cheese, as many layers as you like. The top layer should be sprinkled with water and some grated cheese and the whole thing baked in a medium oven for 20 minutes or so until piping hot and the top layer crisp and golden. Cover with foil if this happens too quickly. Cut in wedges and dig in. Not an elegant dish but good family grub, and largely made from store-cupboard ingredients.