Boil the potatoes in a pan of salted water for about 8-10 minutes - or until they are almost tender. Drain and leave to cool slightly.
Meanwhile, brown the meat well in a splash of oil in a frying pan.
Add the onion, red pepper, celery and garlic and fry until the onion is soft and translucent.
Sprinkle over the spices and stir in the tomato purée, season with salt and freshly ground pepper and heat through thoroughly.
Add the stock and cream and let the sauce simmer gently - while you slice the potatoes.
Grease an ovenproof dish with oil and arrange half the potato slices over the base in a tight layer. Top with half the meat sauce and half the feta, then repeat with a final layer of potatoes, meat sauce, feta and mozzarella.
Gently stir the top layer a little so the cheese mingles with the sauce, then bake in a preheated conventional oven (top and bottom heat) at 200°C for about 25 minutes.
Let the bake settle for 10 minutes before serving - and serve with a fresh green salad and ice-cold crème fraîche, if you like.