Heat the vegetable oil in a large saucepan. Sauté the onion and garlic for a few minutes. Add the bay leaf, chilli powder, paprika and cumin and cook for a further minute.
Add the beef mince and brown. Add the mushrooms, tomatoes and beef stock. Season with salt and pepper. Simmer for 25-30 minutes until the sauce has thickened. Remove the bay leaf and check the seasoning.
Preheat your oven to 180°C. Arrange half the nacho chips in a single layer on one large ovenproof platter or two dinner plates. Spoon half of the mushroom mixture over the nachos. Sprinkle half of the cheese over the top
Arrange the remaining nachos in a layer on top of the cheese. Spoon the rest of the mushroom mixture on top, and sprinkle with the leftover cheese. Pop the nachos in the oven for 10-12 minutes until the cheese has melted and is starting to bubble.
To prepare the salsa: combine the tomato, onion, lime juice and coriander in a bowl. Set aside.
Take the nachos out of the oven and take straight to the table. Serve with a generous dollop of sour cream, guacamole and plenty of salsa.