For the Salmon: Cut the salmon 8 slices, crosswise and lay them out on a work surface. Combine the next 3 ingredients and brush generously on the salmon. Heat a little vegetable oil in a cast iron or heavy skillet over medium high heat and sear the salmon until caramelized on both sides;; about 1 minute on each side. Remove to a platter. Note: The salmon is delicious if it is still warm when the sandwiches are made. However, if you are not going to eat the sandwiches right away, chill the salmon before composing.
To make the vegetables: Place the vegetables in a bowl. Combine the rest of the ingredients in a small saucepan and heat until the sugar and salt are dissolved. Pour the warm pickling liquid over the vegetables and allow them to marinate at least 1 hour and up to overnight. When you are ready to prepare your sandwiches, remove the amount of veggies you need and store the rest in your refrigerator for up to 3 weeks.
To Assemble Sandwiches: Slice the baguette pieces lengthwise, leaving them hinged. Tear a little of the bread out of each half to slightly hollow it.
With a vegetable peeler, cut thin strips of cucumber the same length as the baguette. Make 3 or 4 for each sandwich. If you like, you may sprinkle the cucumber with a little fish sauce or just a dash of salt and sugar.
Spread the inside with mayonnaise and place 2 pieces of salmon on the bottom. Layer the sliced cucumbers, pickled vegetables, sliced jalapenos and cilantro sprigs on top.
Wrap the sandwiches in butcher or parchment paper for travel or just use both hands and eat it immediately.