Put the chicken pieces in a large bowl. Add the garlic and rosemary, sprinkle with a teaspoon of fine salt and pour in the buttermilk. Turn the chicken over to coat well — it needs to be covered by the buttermilk. Cover with plastic wrap and put into the fridge for at least 12 hours, even for over 24 hours. Turn the chicken once or twice to distribute the flavours.
Pour into a colander to drain (you don’t need to keep the buttermilk marinade). Put the flour on a plate and add the paprika and about 1 teaspoon of fine salt. Add pepper, if you like, and mix everything together.
Pour at least 5 cm(2 inches) of oil into a large frying pan over medium heat. Heat until the oil is hot. Pat the chicken in the flour to coat it on all sides, making sure that all the nooks and crannies are covered. Add the chicken to the hot oil and fry until it is crispy and golden. If the chicken seems to be browning too quickly, turn down the heat a little. It is important that the chicken is cooked right through to the bone — use tongs to turn the pieces over a couple of times until you are satisfied that they are deep golden and cooked through. Lift out onto a plate lined with kitchen paper to absorb the excess oil. Serve immediately, with a sprinkling of salt and some lemon wedges to squeeze over the top.