Put the chicken between two pieces of greaseproof paper and flatten using a rolling pin until about 1cm thick.
Put the hazelnuts, parmesan, lemon zest and thyme into a food processor and blend to fine crumbs.
Add the breadcrumbs and pulse quickly to just break up the crumbs, then tip out onto a plate.
Scatter the flour onto a plate and season with salt and black pepper. Dust the chicken in the flour.
Put the beaten eggs in a bowl. Dip the chicken into the egg, then into the hazelnut breadcrumbs, making sure to coat each side thoroughly.
Heat the butter in a large frying pan, add the chicken breasts and fry until golden-brown - about five minutes on each side - basting with the butter as you go.
Drain onto kitchen paper and then finish with a little more parmesan cheese.
To serve, lay the chicken escalope on each plate and drizzle over all the remaining butter in the frying pan, then finish with a squeeze of lemon juice.
Pile the salad leaves alongside with a wedge of lemon.