Slice each chicken breast horizontally through the center, leaving one edge intact.

Open each chicken breast into a flat escalope and place it between baking paper sheets.

Pound each chicken breast evenly to about 1 cm thick.

Place one slice of ham and one slice of Gruyère cheese on one half of each chicken breast.

Season the cheese with black pepper and leave a small border around the chicken edges.

Fold the chicken over the filling and press the edges firmly to seal.

Put plain flour, beaten egg, and fine breadcrumbs into three separate bowls.

Coat each stuffed chicken piece in plain flour and shake off the excess.

Dip each floured chicken piece into the beaten egg until fully coated.

Press each chicken piece into fine breadcrumbs until evenly coated.

Rest the breaded chicken for 20 minutes so the coating adheres.

Preheat the oven to 180°C / 350°F.

Heat neutral oil to a 5–7 mm depth in a large frying pan over medium heat.

Add the cubed unsalted butter and let it melt until the fat foams gently.

Fry the breaded chicken for 4–5 minutes on the first side until deep golden brown.

Turn the chicken and fry the second side for 4–5 minutes, spooning hot fat over it.

Transfer the chicken to an oven-safe baking dish and bake for 3–6 minutes.

Season the cooked chicken with salt, slice it, and serve immediately.