Make the marinade: In a medium bowl, whisk together yogurt, garlic, vinegar, paprika, red pepper flakes and salt. Spatchcock the chicken: Place chicken, breast-side down, on a cutting board.
His spice mixture makes enough for two legs of lamb but it is worth making the entire amount, rather than halving the recipe ... lemon juice and 250g (9oz) of yogurt before spreading it over ...