Preheat the oven to 200°C.
Heat 150ml cream, 150ml milk, and 2 garlic cloves in a pan and season.
Layer 1kg sliced potatoes in a greased dish and pour over the cream mixture.
Bake the potatoes for 45 minutes.
Sear the 900g lamb in a hot ovenproof pan with oil until browned.
Roast lamb in the oven for five minutes and set aside to rest.
Mix 200g breadcrumbs with chopped herbs and a drizzle of oil.
Spread Dijon mustard over the lamb and coat with the breadcrumb mixture.
Return lamb to the oven for 15-20 minutes, then rest for five minutes under foil.
Boil the fennel until tender and remove from the water.
Warm the fennel in a pan with 1 ladle of chicken stock.
Heat oil, vinegar, and sugar, then gently cook tomatoes and thyme for five minutes.
Slice the lamb and fennel and serve with the potatoes and tomato sauce.