Simmer haddock, salmon, bay leaf, and peppercorns in 300ml of milk for 5 minutes.
Flake the cooked fish, discard skin, and strain the milk into a clean pan.
Cook beaten eggs with butter in a frying pan until they just hold together.
Place half the fish on the omelette, transition it to a dish, and top with the rest.
Whisk remaining butter, flour, and reserved milk in a pan to create a smooth sauce.
Pour sauce over the omelette, add cheese, and grill for 3-5 minutes until golden.
Mix lettuce, fennel, and radishes in a large bowl.
Blend all dressing ingredients until smooth and toss with the salad before serving.