Place the potatoes in a pot and cover with cold salted water. Bring to the boil and cook for 15-18 minutes until fork-tender. Drain well.
Add the butter and cream and mash until smooth. Season with salt and white pepper. Cover and keep warm.
The Diane Sauce
Melt the butter over medium heat. Add the garlic and cook for 30-45 seconds until fragrant. Add the tomato paste and cook for 1 minute until slightly darker.
Dissolve the gravy granules in boiling water and pour in while stirring. Add the Worcestershire sauce and cracked black pepper. Simmer for 2-3 minutes until slightly thickened. Stir in the cream and simmer for another 2-3 minutes until glossy. Keep warm on low heat.
The Schnitzel
Butterfly the chicken breasts and flatten to about 1cm thick. Season both sides with salt and pepper.
Set up three bowls: flour, beaten egg and panko breadcrumbs. Coat the chicken in flour, dip in egg, then coat in breadcrumbs. Press firmly so they stick well.
Heat oil to 170°C (340°F). Carefully add the schnitzel and cook for 3-4 minutes per side until golden, crisp, and the chicken is cooked through, reaching an internal temperature of 74°C (165°F). Transfer to a rack and rest for 1 minute.
Plate with mash first, schnitzel on top, and Diane sauce poured over. Finish with parsley and lemon wedges if using.
Chef's Tips
Flatten the chicken to an even thickness before crumbing — this ensures it cooks through evenly in the same time it takes the crumb to turn golden, rather than some parts drying out while others stay undercooked.Press the panko on firmly after dipping — a loosely packed crumb will fall off in the oil instead of forming a crisp, even crust.Keep the oil at a steady 170°C (340°F) throughout frying — too hot and the crumb burns before the chicken cooks through; too cool and it absorbs oil and turns greasy instead of crisp.
Storage & Reheating
Store schnitzel and sauce separately in the fridge for up to 3 days. Reheat schnitzel in the oven or air fryer at 180°C (350°F) to keep the crumb crispy. Reheat sauce in a small saucepan over low heat.