Cut shallots in half. Toss together shallots and next 2 ingredients in a jelly-roll pan; sprinkle with desired amount of salt and pepper.
Bake 45 to 50 minutes or until shallots are light brown and skins are charred, stirring twice. Cool completely in pan on a wire rack (about 30 minutes).
Remove and discard papery skins from shallots and garlic, and coarsely chop shallots and garlic.
Stir together sour cream and next 7 ingredients; fold in shallot mixture.
Add salt and pepper to taste. Cover and chill 4 to 48 hours. Stir before serving.
Add salt and pepper to taste just before serving, if desired.