Blitz 1 tbsp oil, half the lime juice, coriander and garlic with all the lime zest, chilli and ginger in a small blender, then season. Pour this over the chicken and leave it to marinate for 20-30 minutes. Mash the remaining garlic, coriander and lime juice with the avocado. Add the yogurt and season. Heat a griddle pan until very hot, wipe the excess marinade off the chicken and cook for 4 minutes on each side or until cooked through. Pile the guacamole into the bun, top with the chicken and add the lettuce and tomato.