In a large bowl, combine the buttermilk, garlic and 2 tablespoons of salt. With a sharp knife, make shallow, 1-inch-long slashes in the chicken. Rub generously with Tabasco sauce and add to the buttermilk; turn to coat. Cover and refrigerate overnight. Light a grill. Remove the chicken from the marinade and grill over moderate heat, turning often, until the skin is browned and charred in spots and the meat is cooked through, about 30 minutes.
In a shallow dish, toss the cornflakes with the parsley and season with salt and pepper. Brush the chicken with the butter. Using tongs, roll the chicken in the cornflake mixture. Transfer to a platter and serve, passing Tabasco sauce at the table.