Make the spice mix by combining the paprika, cayenne, thyme, garlic granules, onion granules and celery salt in a bowl. Season and mix to combine. Add half the spice mix to a large bowl with the buttermilk and chicken. Mix to coat the chicken, then cover and leave to marinate in the fridge overnight. Reserve the remaining spice mix.
Preheat the oven to 220°C/200°C fan/gas mark 6. Remove the marinated chicken from the fridge. Mix the reserved spices with the flour, and put the beaten eggs, breadcrumbs, and spiced flour in three separate bowls large enough to dip the chicken in.
Take each piece of marinated chicken, dip in the spiced flour first, then the egg mixture, and finally in the breadcrumbs to coat thoroughly. Tap to remove excess crumbs and place on a large baking tray. Once all the chicken thighs are coated, bake in the oven for 40-50 minutes, until dark golden and cooked through.
When the chicken has been in the oven for 15 minutes, bring 400ml water to the boil in a saucepan. Add the rice, cover and cook for 10 minutes. Remove the rice from the heat and leave to steam with the lid on for another 10 minutes.
Remove the lid and fold through the beans, coriander, carrot, cabbage and lime juice, taste and check for seasoning. Serve the chicken with the warm rice salad.