Filling: Trim off the dark green parts of the leeks, then cut the remaining light green and white parts in half, lengthwise. Clean by fanning the layers apart as you rinse. Cut the leeks crosswise into narrow strips. Melt a bit of the butter in a skillet and sauté the leeks for a few minutes, until they start to become more tender. Add the ginger and sauté another minute more. Transfer the leeks to a medium bowl and set in the fridge to cool off.

Cut the tomatoes in half laterally, then squeeze each half gently to remove most of the seeds. Chop the tomatoes to a small dice, and mince the parsley. Remove the skin and any bones from the salmon, chop it into small pieces, then sprinkle the salt over it.

Remove the bowl of leeks from the fridge, which should now be cool enough to not cook the salmon. Add the tomatoes, parsley, and salmon as well as the mustard and cream, to the bowl and stir to combine.

Phyllos: Melt the remaining butter in the now-empty skillet. Unfold the stack of phyllo and lay them out on a clean dishtowel, and preheat the oven to 400°.

Take the top phyllo off the stack and lay it on your working surface with a short end closest to you, then use a second towel to cover the stack. Use a pastry brush to quickly cover the phyllo sheet with butter. Place a second phyllo on top of the first and, again, brush with butter. Imagine a square a half-inch from the front edge of the two-phyllo stack, and a third of the width of the phyllo sheets. Now, draw an imaginary diagonal line through that square to make two triangles, one with an entire side near the front edge and the second with just a tip on that line. Use a one-third-cup measure to scoop out some salmon, and place it in on that second triangle. Fold the left and right long sides of the phyllo into the center, so you have a strip that is one-third of the original width. Fold the front triangle over the salmon, then continue folding "flag-fold" style to wind up with a triangle of salmon with phyllo protecting it on all sides. Place onto a baking sheet and brush a little more butter on top. Repeat until all of the phyllo sheets and/or all of the salmon is gone.

Bake for 20 minutes or until the top is golden brown.

Note: A one-pound package of phyllo dough typically might have eighteen 13" x 18" sheets, so folding the rolls per these directions will give you nine main-dish size servings. To make appetizer-size servings, use one sheet of phyllo per roll, and start by folding that sheet into quarters rather than thirds.