Soak the lox overnight in cold water in the refrigerator, changing the water once.
Cut the lox pieces in half-pound chunks.
Slice the onions
In a mixing bowl place the water, vinegar, sugar and mixed pickling spices. Stir by hand until the sugar dissolves.
Place in a glass bowl, layering them with the onion slices.
Pour the mixture over the salmon and let stay out on the counter top overnight so that the pickling process starts to work.
Next morning refrigerate for 2 days or until ready to use. Serve as is or with the following cream sauce.
In a glass bowl place the sour cream, buttermilk and marinade. Mix well. If it is too thick, add a little extra buttermilk.