Combine apple sauce and sugar; set aside.
Combine half-and-half and marshmallows in top of a double boiler. Place over boiling water and cook, stirring constantly, until marshmallows melt and mixture is well blended. Remove from heat; let cool. Transfer mixture to a large mixing bowl; freeze until firm, but not solid.
Beat frozen mixture until smooth; add applesauce mixture, salt, and lemon juice, beating well. Freeze until firm.
Beat frozen mixture again, and fold in whipped cream. Pour into two 2-cup metal ice trays (with dividers removed). Freeze 3 hours or overnight. Spoon into individual serving bowls, and serve immediately.