Preheat the oven to 200C/Fan180C/Gas Mark 6. To prepare the chicken, place the chicken on a chopping board breast side down. Starting from the tail end cut with a sharp knife or scissors through the flesh and bones along both sides of the backbone about 4-5cm wide all the way up to the head end. Remove the backbone completely. Press the chicken as flat as possible. Score the thighs and drumsticks with a sharp knife and insert 2 metal skewers on either side of the chicken.
In a bowl mix the butter, garlic and chilli flakes. Lift the skin under the chicken breast and spread with half the butter. Repeat with the second chicken breast. Mix the paprika, parsley, salt and pepper and oil together and spread over the skin of the chicken. Squeeze over the lime juice. If time allows marinade for 2-3 hours.
Place the garlic cloves and half the rosemary sprigs in the bottom of the roasting tin. Drizzle with olive oil and season. Place the chicken skin side up on top of the garlic and rosemary.
Place in the oven and roast for 55 minutes -1 hour or until cooked through.
Meanwhile, to make the Caesar salad, toss the bread cubes in the oil and cook in a hot frying pan for 2-3 minutes or until golden and crisp. Remove from the frying pan and drain on kitchen paper.
Melt the butter in a frying pan and add the walnuts and cook for 3-5 minutes. Remove from the frying pan and allow to cool on a plate lined with kitchen paper.
Remove the chicken from the oven. Check the juices run clear by piercing the chicken in the thickest part. If the juices are not clear continue cooking for a further 5-10 minutes. Check again to make sure the juices run clear. Allow to rest for 10-15 minutes.
Place the lettuce leaves on a serving plate. Add the croutons, walnuts and Parmesan and drizzle over the dressing. Serve straight away with the chicken, garnished with rosemary.