With an electric mixer fitted with the paddle attachment, cream the cream cheese until smooth. With the mixer on medium speed, add the sour cream, lemon juice, dill, scallion, milk, salt and pepper. With a rubber spatula, fold in 3/4 of the salmon roe (caviar). Spoon the dip into a bowl and garnish with the remaining salmon roe and sprig of fresh dill. Serve with chips and grilled herb shrimp skewers.