For the quick onion pickle, thinly slice the red onion and place in a bowl. Add in the juice of the lemons, reserving some for the cabbage slaw, and the sea salt and massage gently until slightly tender. Set aside.
Slice the halloumi into thick slices and set aside.
For the speedy red cabbage slaw, slice the red cabbage on a mandolin, grate the carrot and thinly slice the spring onions.
Add the red cabbage, carrot and spring onions to a bowl with the mayonnaise and the rest of the lemon juice. Season with salt and pepper. Mix to combine and set aside.
To make the burger mix, roughly chop the chorizo and blitz in a food processor until smooth. Transfer the chorizo to a mixing bowl and add the chicken mince and fennel seeds. Stir well to combine.
Form into burger patties roughly 8cm in diameter, placing on a plate as you go.
Heat a large non-stick frying pan over a high heat, and toast the burger buns. Set aside.
Add the rapeseed oil to the frying pan and fry the burgers for 3-4 minutes either side until cooked all the way through, transfer to a plate lined with kitchen paper and keep warm.
Using the oil in the pan fry the halloumi slices until golden on each side and remove to the plate with the burgers.
Slice the avocado for the burgers.
To build your burger, first add your lettuce to the bun and top with the red cabbage slaw. Add the chorizo burger, halloumi slices, slices of avocado and onion pickle before finally the top of the bun.