Prepare the avocado cream: Halve the avocados, remove the stones, and scoop the flesh into a blender. Add the sour cream or Greek yoghurt, the juice of one lime, a pinch of salt, and a small handful of coriander. Blitz until completely smooth and silky—you should see a pale green, velvety consistency with no lumps. Taste and adjust the salt or lime juice as needed. Transfer to a bowl and set aside.

Season the prawns: Pat the prawns dry with kitchen paper—this is crucial for a good sear. In a bowl, toss them with the olive oil, smoked paprika, cumin, garlic powder, cayenne (if using), and a generous pinch of salt and black pepper. The prawns should be evenly coated, with the spices clinging to each one. You'll smell the earthy, smoky aroma rising from the bowl.

Cook the prawns: Place a large frying pan over a high heat and let it get hot—a drop of water should sizzle instantly. Add the prawns in a single layer; do not overcrowd the pan. Cook for 2 minutes without moving them. Listen for the vigorous sizzle; when the undersides are golden and slightly charred, flip each prawn. Cook for another 1–2 minutes, until they are pink, opaque, and curled into loose 'C' shapes. Remove from the heat immediately to prevent them from becoming rubbery.

Warm the tortillas: While the prawns rest, heat a dry frying pan or griddle over a medium heat. Warm each tortilla for about 30 seconds per side, until they are pliable and have small brown spots. Stack them on a plate and cover with a clean tea towel to keep them soft and warm.

Assemble the tacos: Lay two tortillas on each plate. Divide the shredded cabbage among them, creating a small bed for the prawns. Arrange 4–5 prawns on top of the cabbage on each taco. Drizzle generously with the avocado cream. Top with a few slices of red onion and jalapeño, if using. Finish with a squeeze of fresh lime juice and a scattering of extra coriander leaves.

Serve immediately: The tacos are best enjoyed right away, while the prawns are still warm and the tortillas are soft. The contrast of the cool cream and the hot, spiced prawns is the moment everything comes together.