Combine first 3 ingredients in a large heavy saucepan; cook over medium heat, stirring constantly, until cream cheese and marshmallows melt. Remove from heat.
Add gelatin, stirring until dissolved. Stir in pineapple and pecans. Chill until the consistency of unbeaten egg white.
Fold in whipped cream. Pour mixture into 12 lightly oiled 1/2-cup molds. Cover and chill until firm. Unmold onto lettuce-lined salad plates. Garnish, if desired.