Begin by prepping your vegetables: for large bok choy, cut and wash 10 leaves. For small, rinse and leave whole. I like to julienne my carrots and celery but you can chop them however you like. Chop green onions on a bias and leave enoki mushrooms long and beautiful.
Using a deep enough pan to allow the salmon to be entirely immersed, sautee the onions and garlic until transluscent. Sprinkle with salt and pepper. Use the entire piece of lemon by squeezing the juice over the onions then leaving the rind in the pan.
Fill the pan half way with water and add the miso and bouillion. Place fish skin side down and top-up with enough water to submerge it. Cook 6-10 minutes depending on the thickness of the fish (I like medium-rare so usually stick to 6 minutes).
In the final 2 minutes of cooking, add the carrots, celery and bok choy.
Remove the salmon from the broth and place in a shallow bowl. Remove lemon pith from the broth and add enoki, green onions and watercress to quickly heat through (about 20 seconds). Arrange vegetables around the salmon and pour the broth over top.