Preheat the oven to 200°C/fan 180°C/gas mark 6. Place the chicken in a bowl with the paprika, lemon juice and ½ tbsp olive oil. Cover and place in the fridge to marinade for at least 20 minutes.
Tear the ciabatta into small rustic chunks. Place on a baking tray and drizzle with 1 tbsp olive oil and seasoning, then bake for 12-15 minutes until golden and crisp.
Heat a griddle pan over a medium-high heat and cook the chicken breasts for 5-6 minutes on each side, until there are dark griddle marks all over. Place in the oven for a further 8-10 minutes to ensure they are cooked through, then set aside to cool slightly before slicing.
Halve the peaches and remove the stones, then cut into quarters. Brush with the remaining olive oil. Heat a griddle pan over a medium-high heat and cook for 2 minutes on each side, until there are griddle marks all over.
Scatter the rocket on to a platter. Add the chicken and peaches, then tear over the prosciutto slices. Top with the croutons and drizzle over the balsamic vinegar.