1) In the bowl of an electric mixer fitted with a paddle attachment, cream the cream cheese until smooth. With the mixer on medium speed, add the sour cream, lemon juice, dill, spring onion, milk, salt, and pepper.
2) With a rubber spatula, fold in 3/4 of the salmon roe. Spoon the dip into a bowl and garnish with the remaining salmon roe and sprigs of fresh dill.
3) Serve with chips, toasts, or crackers.