Preheat the oven to 220 °C.
Boil the potato slices in salted water for a few minutes and strain them in a sieve.
Heat an ovenproof saucepan or casserole dish on the hob and add the olive oil, garlic, onion, fennel and fennel seeds and sauté for about 5-10 minutes until soft. Then remove from the heat.
Place the trout fillets, skin side up, on top of the onion-fennel mixture. Mix the whipped cream, Parmesan cheese and anchovies, season with salt and pepper and pour over the fish.
Mix the potato slices and fennel slices with a tiny bit of olive oil, salt and pepper and layer on top. Bake in the oven for 15 minutes.
Sprinkle the breadcrumbs and a tiny bit of grated Parmesan on top and bake for another 5-10 minutes, until a golden brown crust is formed.
Garnish with the lemon halves and serve.