Using either a handheld or stand mixer fitted with the flat beater, whip the cream cheese until smooth. Add the sour cream, lemon juice, scallions, and horseradish and mix until combined. Add the salmon and mix in. Mix in one tablespoon of milk and check the consistency. If you want it a little thinner, add another. Once you're happy with the dip, fold in about 3/4 of the caviar and reserve the rest for topping the dip.
Serve the dip with crackers, cucumber slices, or toast points. The dip can be served immediately or can be held in the refrigerator for up to one day.
You can order salmon caviar online if needed.
I prefer to use wild Alaskan salmon. I find the flavor and the color to be the best around.
Some extra minced scallions and smoked salmon sprinkled over the top of the dip is nice too.