Heat the oil in a pan. Sauté the shallot and garlic. Add the rice, cook while stirring until translucent. Add the lemon zest and thyme. Pour in the wine and lemon juice, reduce completely. Gradually add the stock, stirring frequently, so that the rice is always just covered with liquid, simmer for approx. 25 mins. until the rice is creamy and al dente. Stir in the butter and cheese.
Pat dry the fish fillets, season. Empty the flour into a shallow dish. Heat the clarified butter in a non-stick frying pan. Coat the fish fillets in flour in batches, shake off the excess flour, press the rest down firmly. Heat the butter in a non-stick frying pan. Place the fish fillets in the pan (skin side up), fry for approx. 1 min. Turn the fillets, add the sage and fry for a further 2 mins. Serve the fish fillets with the lemon risotto.