Preheat your oven to 200°C (180°C fan) or 400°F. While it heats, place a large frying pan over medium-high heat and add the olive oil. When the oil shimmers and a small piece of onion sizzles immediately, you're ready to begin.

Cook the onion and garlic. Add the diced onion and cook for 4-5 minutes, stirring occasionally, until the pieces turn translucent and softened, and you can smell that sweet, savoury aroma. Add the minced garlic and cook for another minute, until fragrant—don't let it brown too much, or it will turn bitter.

Brown the beef mince thoroughly. Tip the mince into the pan and break it apart with a wooden spoon. Let it cook undisturbed for 2 minutes to develop a deep brown crust, then stir and repeat. The mince is ready when it's no longer pink, and you hear a steady sizzle rather than a watery hiss. This should take about 6-8 minutes. Drain off any excess fat, leaving about a tablespoon in the pan for flavour.

Build the sauce. Stir in the cumin, smoked paprika, cinnamon, and oregano. Cook for 30 seconds, stirring constantly, until the spices smell toasted and aromatic. Add the chopped tomatoes, tomato purée, and beef stock. Stir well, scraping up any browned bits from the bottom of the pan—those little dark flecks are pure flavour. Bring the mixture to a gentle simmer; you'll see small bubbles breaking the surface. Reduce the heat to low and let it cook for 10-12 minutes, stirring occasionally, until the sauce thickens and turns a deep, rich reddish-brown. The texture should be thick enough to coat the back of a spoon but not dry.

Season and rest the beef. Taste the beef mixture and add salt and pepper as needed. Remove the pan from the heat and let it sit for 5 minutes. This resting time allows the flavours to meld together and the meat to absorb the sauce fully.

Assemble the nachos on a baking tray. Spread half the tortilla chips in a single, even layer on a large oven-proof tray or dish. Spoon half the beef mixture over the chips, making sure to distribute it evenly—don't just pile it in the centre. Sprinkle with half the grated cheese. Repeat with the remaining chips, beef, and cheese. If using fresh jalapeño slices, tuck them in between the layers now.

Bake until bubbly and golden. Place the tray in the preheated oven and bake for 10-12 minutes. You'll know it's done when the cheese is completely melted, bubbly, and starting to turn golden brown at the edges. The chips around the perimeter will be slightly darker and crisper, while the centre stays satisfyingly tender. Remove the tray from the oven and let it rest for 2-3 minutes—this keeps the layers from sliding apart when you serve.

Add fresh toppings and serve. Dollop spoonfuls of sour cream over the hot nachos, scatter the diced avocado, spring onions, and fresh coriander, and finish with a generous squeeze of lime juice. Serve immediately straight from the tray, with extra lime wedges on the side.