Pour the water into a large frypan, add in the onions, lemon, bay leaf, peppercorns, and parsley stalks and bring the liquid to the boil.
Add in the fish, making sure that most of the fish is covered with the poaching liquid. Bring the liquid back to the boil, lower to a simmer and cook the fish for 3-4 minutes on both sides until the fish can be easily flaked apart with a fork. Remove the fish from the liquid with a slotted spoon and discard the liquid.
Cool the fish just enough so that you can flake it into chunks, then toss the fish with the spinach to slightly wilt the spinach.
For the salad, combine the beans with the chopped celery, chopped garlic, peeled zucchini, red onion and parsley.
Whisk the sour cream with the verjuice, lemon juice and season it with salt and pepper. Add the slightly warm fish and spinach with the beans and pour over the dressing tossing the salad gently to combine the flavours. Serve the Poached Snapper Salad warm.