Bring a small pot of salty water to boil. Blanch the watercress until the stems are very soft to the touch. Shock in ice water. Remove watercress from the shocking bath. Squeeze as much water out of the watercress by hand, and then by wrapping up in a kitchen towel. Chop the watercress as finely as possible by hand. Place the chopped watercress in a blender, and slowly add the canola oil. Remove the watercress oil from the blender and refrigerate.
Combine the smoked salmon, shallots, ginger, chives, cucumber and Ginger Vinaigrette in a mixing bowl. Season to taste with salt and pepper. Place a mold of your choice on the plate of your choice, and pack some of the smoked salmon mixture into the mold. Top with 2 tablespoons of the creme fraiche. Garnish, if so desired, with 1 teaspoon of the optional caviar. Repeat 3 times.
Garnish each plate with a few decorative squiggles of the watercress oil.
Place the ginger and canola oil in a small pot. Bring to a simmer over low heat. Remove from heat and let stand 12 hours. Strain the oil through a cheesecloth lined strainer. (The ginger oil may be kept in the refrigerator for 3 months.)
Combine the ginger oil with as much vinegar and mix well.