Place the turkey in a bowl with the cornflour, fajita spice, salt and pepper, toss together to coat the turkey.
Heat the oil on a high heat in a large frying pan (skillet) and add the turkey to the pan. Cook, turning a couple of times until golden brown all over. This should take about 6-8 minutes. Try not to turn too much, as the turkey won't brown as quickly. Remove from the pan and place in a bowl.
Add the black beans, passata, garlic and a pinch of salt and pepper to the pan (you can use the same pan) and heat through for 3-4 minutes until bubbling. Turn off the heat.
Pre-heat your grill (broiler) to a high heat.
Layer half of the tortilla crisps in a large (ideally round) oven-proof dish. Top with half of the beans and half of the turkey. Top with all but a handful of the remaining tortilla crisps, the remaining beans and remaining turkey. Sprinkle the cheese all over the top, ensuring the tortilla crisps are well covered (if they're sticking out too much, they'll burn).
Place under the grill until the cheese is melting and bubbly. Remove from the grill, decorate the edges with the remaining tortilla crisps, and place back under the grill for a few seconds to warm through and lightly brown them.
Remove from the grill, then scatter over the tomatoes, red onion slices, avocado chunks, spring onions and jalapeno slices. Sprinkle on the chopped coriander and serve.