For sour cream-dill dressing, combine all of the ingredients and mix well. Chill until serving time.
For waffles, combine all waffle ingredients. It should be the consistency of very thick pancake batter. Preheat a waffle iron and brush the surface with melted butter. Prepare the waffles according to the machine instructions and cook until golden and crisp. Trim to 3 inches in diameter. Repeat with remaining batter. Keep the prepared waffles warm in a 250 degree oven.
Assembly: Spray the inside of a stack cylinder with vegetable spray and place on a small serving platter. Place a waffle round in the bottom of a cylinder and layer with 1 tablespoon dressing, followed by 1 tablespoon green onions and 11/2 ounces salmon. Repeat twice for each stack, using 3 waffles per stack. Press down on the stack gently but firmly and remove the cylinder. Garnish with a dollop of dressing and a teaspoon of caviar. Sprinkle minced green onions around base of stack and serve.
Recipe courtesy of Deborah Fabricant, author Stacks: The Art of Vertical Food