Chicken Cordon Bleu

Steps

1. 1
   Heat the oven to 200°C (fan 180°C) and line a baking tray with baking paper.
2. 2
   Butterfly each chicken breast by slicing it horizontally almost all the way through, open it like a book between two sheets of cling film and pound it with a meat mallet to an even 5 mm thickness.
3. 3
   Season the chicken lightly with salt and pepper, cover each piece with a quarter of the ham and cheese, leaving a 1 cm border, then roll it up tightly from the short end, tucking in the sides so no cheese is exposed.
4. 4
   Wrap each roll tightly in cling film, twisting the ends like a sweet wrapper, and chill for at least 30 minutes — a firm, sealed roll keeps its shape and stops the cheese leaking out.
5. 5
   Set up three shallow dishes: the flour; the eggs beaten with the mustard and a pinch of salt; and the breadcrumbs.
6. 6
   Unwrap the rolls and coat each one in flour, shaking off the excess, then in egg, then press it firmly into the breadcrumbs; for an extra-sturdy crust, dip it in egg and crumbs a second time.
7. 7
   Heat the oil and butter in a frying pan over medium-high heat until the butter foams, then fry the rolls for 2–3 minutes, turning, until golden on all sides.
8. 8
   Transfer them to the tray and bake for 18–20 minutes, until the crust is deep golden and the centre reaches 74°C on a thermometer; to skip frying, spray the crumbed rolls with oil and bake for 30–35 minutes instead.
9. 9
   Rest for 5 minutes so the cheese sets slightly, then cut each roll in half on the diagonal and serve with lemon wedges.