Remove all excess fats from the chicken thighs and pat dry.
In a bowl, mix the buttermilk marinade together and add in the chicken thighs. Coat well with mixture and cover to marinate in the fridge for 2 hours.
Prepare the slaw while the chicken marinates, but do not mix the condiments in yet. Place it in the fridge until you are ready for it.
Slice your tomatoes, lettuce, and any other veggies you want to add and place them in the fridge.
Preheat the oil in a deep large pan at 350 F.
In another shallow plate or bowl, mix together the breading mix.
Remove the chicken from the buttermilk marinade, allowing any excess liquids to fall off, then dredge it into the flour mixture.
Coat the whole chicken thigh well with the flour mixture, patting down the flour onto the chicken with your palms to firmly pack the flour coating on the chicken.
Place on a plate or pan and repeat the process for the other thighs.
Once the oil is hot enough, add the chicken pieces into the pan, leaving space between them.
Fry them on each side for about 4 minutes, or until cooked through and golden brown with an internal temperature of 165 F.
Remove the chicken pieces and place on a rack for a few minutes to rest and drain any excess oil.
Mix the condiments into the slaw and prepare the slaw.
Place the bottom of the brioche buns on a plate and arrange the chicken burger with whatever ingredients you prefer. Start with lettuce always to prevent the bread from sogging.
Serve along side with some fries or favorite side.