Prepare 3 dishes : 2 teaspoons of flour in the first one, 1 beaten egg mixed with 1 teaspoon of olive oil in the second one and hazelnut powder in the third one.
Salt the cod filets and coat them on both sides successively in the 3 dishes (after the first one, tap the fish filets to get rid of the excess of flour).
Heat a frying pan with little butter and 1 olive oil teaspoon and when melt and slightly brown, cook the fish during 5 minutes on each side (carefully check that it does not burn). This way of cooking is called "à la meunière" in French.
In the meantime, pour in a saucepan the cream, lemon juice, a few crushed hazelnuts, reduce it to half quantity and then add the chopped fresh herbs.