BEAT cream cheese and shredded cheese in medium bowl with electric mixer on medium speed until well blended.
STIR in mustard, bacon and 2 Tbsp. of the onions. Transfer to serving bowl, if desired; cover.
REFRIGERATE several hours or until chilled. Let stand at room temperature 30 min. before serving. Sprinkle with the remaining 1 Tbsp. onions. Serve with the crackers.