Place the chipotle, mayonnaise, sour cream and lime zest in a small processor and process until well combined.
Place beef mince in a medium bowl and season with salt and pepper mix until well combined. Divide mix into four and shape in patties. Transfer to a baking tray lined with baking paper and place in the fridge for about 15 min to firm slightly.
Place chorizo in a food processor bowl and blitz until finely chopped.
Heat vegetable oil in a large non-stick pan on medium-high heat and fry chorizo for 2-3 minutes until crisp and starts to resemble crumbs. Strain oil and drain crumbs on paper towel.
Preheat BBQ or char grill pan over medium heat.
Brush patties with a little vegetable oil and grill for 3-5 minutes each side until charred. Top with cheese, remove from heat, keep warm and allow to rest.
Brush prawns with a little vegetable oil and season well with salt and pepper. Grill prawns, in batches, for 1-2 minutes per side or until golden and cooked. Keep warm.
Toast cut sides of buns on the bbq for 30 seconds -1 min until slightly charred, then brush with butter.
Top with patty, watercress, pickles, 3 prawns and chorizo crumbs. Spread 1 tablespoon of chipotle mayonnaise on top half of bun, place and serve with fries and extra chipotle mayonnaise.