Preheat the oven to 190°C.
Remove the mini-fillets from the chicken breasts and butterfly the breasts with a knife.
Flatten the chicken breasts and mini-fillets using a mallet or rolling pin.
Mix the parsley, butter, garlic, mustard, salt, and pepper in a bowl.
Shape the butter into four pieces and chill in the fridge until set.
Place a butter roll in each breast, roll tightly, and seal gaps with the flattened mini-fillets.
Dredge the rolls in flour and chill in the freezer for 3 minutes.
Whisk the egg and milk together in a small bowl.
Coat the floured chicken in the egg mixture and then roll in breadcrumbs.
Chill the breaded chicken in the fridge for 30 minutes.
Heat 120ml of oil and fry the chicken for 2 minutes until golden.
Transfer the chicken to the oven and roast for 12 to 14 minutes.
Drain on kitchen towels and serve with mashed potato, green beans, and lemon.