Poaching the Fish: Place the fish in a wide, deep skillet and cover with water by about 1-inch (2.5 cm). Add scallions, lemon slices, peppercorns, bay leaf and a big pinch of salt. Bring to a simmer over medium heat; you want the water to be barely simmering. By the time the water comes to that simmer, check the filet. You want to cook it just until it is opaque throughout and it might be done more quickly than you imagine. I often bring the water to a simmer, then turn the heat off, cover the pan and allow the fish to sit for a few minutes, then check again. It will all depend on the thickness of your fish and how cold the fish was at the beginning. An approximation is 5 to 10 minutes per inch of fish, but again, best way to tell is to use a visual assessment.

Gently remove fish from the water with a slotted spatula. It can go directly on a serving plate, you can dab it on and off a wad of paper towels briefly and/or you can easily peel off the skin, if you like. If you are serving the fish without the cucumber scales, simply serve hot, warm temperature or even a little chilled with Dill Sauce alongside.

For the Optional Scales: Trim and discard the ends of the cucumbers. Slice crosswise paper thin; this is most easily accomplished with a mandoline, but you can also use a very sharp chef’s knife. Arrange the cucumbers as seen in images, slightly overlapping in each row and from one row to the next. If you have a whole fish, start at the tail.