Place a chicken breast between 2 pieces of baking parchment and use a rolling pin or meat mallet to bash it firmly, creating a steak around 1cm thick. Repeat with the remaining breasts, then season the chicken well on both sides with salt and pepper.
Place the flour onto a plate and the breadcrumbs onto another, then beat the egg in a shallow bowl with the Dijon mustard. Take each piece of chicken and coat it in flour, followed by a coating of egg, then lay onto the breadcrumbs, making sure it is completely coated. Place onto a tray and repeat with the remaining chicken.
Pour 3cm depth of oil into a deep frying pan. Heat the oil to around 180ºC on a kitchen thermometer, or use a piece of bread to test the temperature. It should sizzle and turn golden after 30 seconds.
Add a schnitzel to the pan (or cook 2 if your pan is large enough) and fry for 2-3 minutes on each side, until golden brown and cooked through with no pink meat in the middle. Place onto a sheet of kitchen roll to blot any excess oil, sprinkle with sea salt flakes, then repeat with the remaining schnitzels.
Keep any cooked schnitzels warm on a wire rack in a low oven (about 150ºC, gas mark 2). Serve with a wedge of lemon, sprig of parsley and a good dollop of wild cranberry sauce to cut through the richness.
