Brown the beef: Heat a large frying pan over a medium-high flame. Add the mince and cook, breaking it apart with a wooden spoon, until it turns a deep brown colour and releases a rich, savoury aroma — about 6–8 minutes. You'll hear a satisfying sizzle as the moisture evaporates. Drain off any excess fat.

Sweat the aromatics: Add the diced onion and minced garlic to the pan with the beef. Cook for another 3 minutes until the onion softens and becomes translucent and fragrant. Stir in the cumin, smoked paprika, and oregano — the spices will bloom and smell wonderfully warm and earthy.

Build the sauce: Pour in the tinned tomatoes, beef stock, and tomato purée. Stir everything together and let it simmer for 2 minutes until the sauce thickens slightly and turns a rich brick-red colour. Taste and season with salt and pepper.

Layer the casserole: Lightly grease the inside of your slow cooker. Spoon a thin layer of the beef sauce across the bottom — just enough to coat it. Place a single layer of tortillas on top, tearing them to fit if needed. Spread one-third of the remaining beef mixture over the tortillas, then scatter over some black beans and sweetcorn. Sprinkle with a handful of cheese. Repeat these layers until you run out of ingredients, finishing with a generous final layer of cheese on top.

Cook low and slow: Secure the lid and set your slow cooker to low for 7 hours or high for 4 hours. During cooking, the kitchen will fill with a comforting, spicy-sweet scent. The cheese on top will melt into a bubbly, golden crust that looks irresistible.

Rest before serving: Once the timer goes off, switch the slow cooker off and leave the casserole to rest, uncovered, for 10 minutes. This allows the layers to set slightly so you get clean, distinct portions rather than a sloppy mess. The surface should feel firm to the touch, and the edges will be lightly caramelised.

Garnish and serve: Scatter fresh coriander over the top if you like. Scoop generous portions onto plates — you'll see distinct layers of tender beef, soft tortillas, and oozy cheese. Serve immediately.