Mix the chicken flour ingredients together. Flour the chicken thighs and set aside in the fridge for an hour to create a glue like coating.
Remove from the fridge and re-coat the thighs in the remaining flour. Place in a hot pan with a good amount of oil. Cook gently for 5 minutes on each side until golden brown and crispy. Check temperature with a skewer, it should be hot to touch.
To make the mayonnaise, hand blend the egg, mustard, vinegar in a container. Slowly add the oil, while blending, until a thick emulsion forms.
While the chicken is frying, mix the mayonnaise, ketchup, mustard, jalapenos and pickles. Half the brioche buns and arrange for assembly. Spoon the sauce onto the base of each bun.
Melt the butter and add the spice blend, cook over heat for 1 minute. Remove the chicken from the pan when ready and season in the spiced butter.
Place the two cheese slices on top of each thigh when warm and transfer them to the toasted bun. Season lettuce with salt and pepper and place it on the melted cheese. Top off the sandwich with the second half of the bun and serve.
