Poaching a whole fish makes for a very impressive and relatively painless main course for dinner parties. It’s (sort of) a one-pot dish, well, one fish kettle to be precise. This delicate cooking method, when done correctly, highlights the pure flavour of the fish – in this case ocean trout – unadulterated by oil, which often pervades the flesh when frying or roasting.
If you intend to poach whole fish often, it’s a good idea to invest in a fish kettle. Available from kitchenware stores, this long, narrow saucepan, with a lid, is especially useful for cooking large fish. It contains a perforated insert on which the fish sits, enabling it to be easily lowered into and raised from the poaching liquid. Firm-fleshed fish such as salmon, trout and blue-eye trevalla are excellent candidates for poaching, as some of the finer-fleshed varieties tend to become waterlogged and break apart.
Fish can, of course, be poached in salted water, however, a court bouillon is most commonly used. This is little more than a fancy name for a simple stock of onion, celery, parsley stalks, bay leaves and sometimes a combination of other herbs and spices. An acid such as vinegar or lemon juice is a pleasant addition, particularly when poaching an oilier fish such as salmon or ocean trout. The best way to infuse more subtle flavours into the fish is to stuff them into the fish cavity and gently truss the fish. Not only does trussing keep the stuffing inside, but the fish will keep its shape during cooking and the taut shape will cook more evenly.
During the gentle process of poaching, the liquid should be kept at around 80 degrees. If you don’t have a thermometer, look for small bubbles rising and gently breaking on the surface. The delicate fish protein needs this gentle heat to help keep the flesh light and flaky.
Another tip is to stop poaching just before the fish is cooked (adjust according to size of fish), turn off the heat and let it rest in the liquid to finish cooking. To test if the fish is ready, the most reliable method is to make a slit at the backbone and lift the flesh closest to the bone to check that the colour is not too pink. This may not be for the purist but it works, plus, it’s a lot easier than explaining to your guests why the fish isn’t cooked properly. The best way to serve the fish is to gently peel back the skin using your fingers or a knife, discard skin, then flake the flesh off the bone in large chunks.