Heat the chicken stock to boiling in a saucepan, then reduce the heat and hold at a simmer.
Heat the half the butter in a large sauté pan or skillet over medium heat. Sprinkle the fish with salt and pepper, add it to the pan, and sauté it quickly. If you are using crab-meat, just warm it in a little butter for a minute. If you don’t have a very large pan, cook it in batches.