In a bowl combine the lemon zest, dill, parsley, chervil and black pepper. Season the fish with 1/4 teaspoon of the salt, then lightly brush each piece with 1 teaspoon of the Dijon mustard on one side. Firmly press the mustard-coated side of each drum fillet into the lemon-herb mixture.

In a skillet (nonstick is useful here) heat the vegetable oil. Place fillets, coated side down, into the hot oil for 3 to 4 minutes or until crust turns golden brown. Flip and continue to cook for 3 minutes longer or until the fish flakes easily.

Meanwhie in a separate pan, place the Bok Choy cut side down. Add a little water to the pan to steam the Bok Choy until just tender, about 7 minutes. Remove the Bok Choy from the pan and toss in a bowl with olive oil and season with salt and pepper.

When ready to serve, divide the Bok Choy among 4 plates and place 1 fish fillet over the top of each serving. Drizzle with lemon juice and extra-virgin olive oil to taste.