Black Bean Tostadas with Avocado Slaw

Heat the oven to 400°F (200°C). Brush both sides of each tortilla lightly with about 15 ml of the oil total, sprinkle with salt, and lay flat on two sheet pans without overlapping. Bake 5 minutes, flip, and bake another 4–6 minutes until rigid and golden. They crisp further as they cool on a rack.

Heat the remaining 30 ml oil in a skillet over medium heat. Cook the onion 5–6 minutes until soft and translucent, add the garlic, cumin, and chili powder, and stir 30 seconds until fragrant. Add the beans and stock, simmer 3 minutes, then mash with a potato masher or fork to a mostly smooth, spreadable paste. Cook 2–3 minutes more, stirring, until it holds its shape. Season with salt.

Scoop one avocado into a large bowl and mash it with the juice of both limes and a good pinch of salt until creamy. Dice the second avocado. Add the cabbage, jalapeño, and cilantro to the mashed dressing and toss until evenly coated, then gently fold in the diced avocado. Rest 5 minutes so the cabbage softens slightly.

Spread about 3 tablespoons of warm beans over each shell, leaving a thin border. Pile on the avocado slaw, scatter with cotija, and serve at once with extra lime wedges. Assemble at the table so the shells stay crisp.