Ingredients
4 brioche burger buns 
¼ Iceberg lettuce 
500ml flavourless oil 

Ingredients for the chicken 
300ml buttermilk 
Mexican seasoning 
8 boned out chicken thighs or 4 chicken breasts 
150g plain flour 

Ingredients for the Mexican style seasoning 
1 tsp chilli powder (ancho if you have it) 
½ tsp Chipotle chilli flakes 
¼ tsp onion powder  
½ tsp garlic powder  
¼ tsp Tajin (optional) 
¼ tsp chilli flakes  
¼ tsp dried oregano  
¼ tsp ground cumin  
½ tsp smoked paprika  
¼ tsp salt  
¼ tsp ground black pepper  
¼ tsp sugar  

Ingredients for the chipotle mayo 
1 tsp chipotle chilli flakes  
1 tbsp boiling water  
120ml mayonnaise 
Salt 

Ingredients for the guacamole 
2 ripe avocadoes 
3 heaped tbsps of sour cream 
Juice of ½ a lime 
½ tsp of salt 

Method
Put the buttermilk and all but 1 tsp of the Mexican seasoning into a non-metallic bowl and mix.   

If you are using chicken breasts then take them one at a time and put between 2 pieces of greaseproof paper and with a saucepan very carefully bash your chicken a little so they are a little thinner, this is essential to ensure that your chicken is thoroughly cooked through and golden.  Put the chicken into the buttermilk and ensure the chicken is completely covered with the buttermilk.  Cover with cling film and put into the fridge for 1-3 hours. 

For the mayo, in a very small bowl put the boiling water over the chipotle flakes and leave to one side. 

When you are ready to cook.  Put your oven on to 180c and put a greaseproof lined lipped baking tray into the oven. 

Put the oil into a wok ensuring it is not more than half full and warm over a medium heat to 175c.  If you do not have a thermometer then a piece of bread should go golden in 30-40 seconds.  If you look at the oil you can see it shimmering as it gets to temperature.  The thing to remember here is that your chicken will look quite golden very quickly.

While the oil heats up finish off your chipotle mayo by adding the mayo to the softened chipotle flakes and some salt. 

Make your guacamole by cutting your avocado in half long ways and removing the stone. Scoop the flesh out into a dish and roughly mash with a fork, for this some small pieces of avocado are nice. Add the other ingredients and stir. Check the seasoning and adjust if necessary. Cover with clingfilm as avocado can go brown very quickly. 

Make your seasoned flour by putting the flour and the remaining spice mix into a dish, take your chicken out of the buttermilk and put into the flour and thoroughly coat with flour one at a time.  Very carefully fry two at a time.  Very carefully put your chicken into the hot oil being very careful to not splash yourself.  Cook for roughly 5 minutes until the batter is golden.  When your first 2 pieces of chicken are golden, take out and drain on kitchen towel and then put into the oven on your lined tray and turn the oven off.  Put the next two pieces in and cook until golden. 

Meanwhile toast your buns and shred your lettuce.  On the bottom half of your bun add some chipotle mayo and lettuce.  On the top half put some guacamole. 

Check your chicken is cooked all the way through (I do this by taking the thickest one and slicing it in half.  If not cooked just put into the oven for 5 minutes. 

To serve top your bottom bun with the chicken and top of the bun.