Slice each chicken breast fillet through the centre to form 2 equal sized halves. This will produce 8 pieces in total.
Place each piece between non-stick baking paper and flatten with a mallet or heavy rolling pin until very thin.
Dust evenly with seasoned flour, shaking away excess. Dip into egg and then coat with breadcrumbs, pressing to adhere.
Lay coated chicken on a non-stick baking paper lined tray and chill for at least 20 minutes to set the crumb.
Meanwhile, make Grape Tomato Slaw.
Whisk mustard and juice together until smooth. Season with sea salt and black pepper.
Add tomatoes, cabbage and tarragon and toss until evenly coated in the dressing. Set aside.
Place half the oil and half the butter together in a large, heavy-based frying pan on medium heat. Once butter is foaming, cook half the chicken schnitzels for 3 minutes each side until cooked through and golden. Transfer to a plate.
Wipe pan clean with kitchen paper towel. Cook remaining chicken in remaining oil and butter.