Combine the chestnuts, preserved lemon and butter and season to taste. Peel back a little of the skin of the turkey breast to make a pocket big enough for you to smear the chestnut stuffing over the meat. Cover the stuffing with the skin again and tie with kitchen string to secure.
Bake in the oven 30 minutes.
Turn the oven down to 180 degrees C. Smear extra butter over the turkey breast, season with salt and pepper and wrap in banana leaves, securing with string. Return to the oven and bake a further 15 minutes.