Cut each chicken breast in half. One at a time, place breast halves between two sheets of waxed paper and pound flat. Spread some mustard down the center of each breast, and then layer with 1 ham slice and 1 cheese slice. Fold breast half around the filling; beginning with one long side, then short sides, finishing with a long side making sure the filling is completely covered. Press edges together and roll each piece as it is finished in a sheet of waxed paper. Season flour with salt and pepper. Beat egg lightly with 1 teaspoon water. Line up a plate with flour, a shallow dish with beaten egg, and a plate with bread crumbs. One by one, roll each piece in flour to coat, then dip in egg, coating completely, and roll in bread crumbs, pressing crumbs into egg coating. Place chicken pieces on a tray and refrigerate for one hour. Heat enough peanut oil in a large frying pan so that it comes up half way. Fry chicken pieces, two at a time, in hot oil, until browned evenly on all sides; about 2 minutes each side. Remove from oil, drain on paper towel and place in a non stick baking dish. Bake at 180ºC or 15 minutes.