Peel off the leaves from the rosemary stalk and bash together with the oil, salt & pepper in a mortar & pestle.
Rub all over the chicken.
Place some extra sprigs of rosemary and the bread on the bottom of a cast iron pan (or a heavy based roasting dish), place the chicken over & bake until cooked and crispy. (The bread will soak up all the chicken juices & oils and these will be used as the croutons in the salad)
Remove from oven, lay over the pancetta/bacon, return to oven & cook until pancetta/bacon is crispy.
Place the anchovies, a little of the anchovy oil & the garlic in a mortar and pestle and smash together well.
Add creme fraiche, lemon juice & parmesan cheese. Mix well then add the oil and mix until combined & smooth.
Place th lettuce leaves into a bowl.
Take the chicken from the oven and tear off the meat then rustically chop up with the pancetta/bacon & bread (reserving some bread & pancetta/bacon for topping).
Mix the chicken, pancetta/bacon and bread in with the Cos leaves and drizzle over the dressing,
Sprinkle over the reserved bread & pancetta/bacon & shave over some fresh parmesan.