For the chicken escalopes, sandwich each chicken breast between two sheets of cling film. Using a rolling pin, flatten each chicken breast until it has widened and become thinner (this is called an escalope). Remove and discard the cling film. Season the chicken escalopes with the chopped sage and black pepper.
Tip the flour into a bowl. Beat the eggs and milk together in a separate bowl. Sprinkle the breadcrumbs onto a plate.
Dredge each chicken escalope in the flour and shake off any excess. Dip each floured escalope in the egg and milk mixture, then dredge it in the breadcrumbs until completely coated.
Heat half of the butter in a frying pan over a medium to high heat. Add two of the breaded chicken escalopes, in batches, and fry for 4-6 minutes on each side, or until the breadcrumbs are crisp and golden-brown and the chicken is cooked through (the juices will run clear when the chicken is pierced in the thickest part with a skewer). Remove the breaded escalopes from the pan and keep warm.
Repeat the process with most of the remaining butter and the remaining two chicken escalopes. (Reserve a little of the remaining butter.)
Heat the remaining butter in the frying pan over a medium heat. When the butter has turned a pale golden-brown, squeeze in the lemon juice and stir to combine. Remove from the heat.
For the salad, in a large bowl, mix together the olive oil and balsamic vinegar, to taste, until well combined. Add the rocket leaves and mix well to coat the leaves in the dressing.
To serve, place one chicken escalope into the centre of each of four serving plates. Pour a little of the lemon butter over each escalope. Pile the dressed rocket leaves alongside and sprinkle over the parmesan.