Melt marshmallows in milk over hot water; stir until smooth. Let stand over hot water until ready to use.
Add salt to egg whites; beat until frothy. Add sugar gradually, beating until stiff peaks are formed. Fold in marshmallow mixture. Spread gently over hot cream filling.
Broil 8" to 10" from heat until delicately browned, 2 to 3 minutes. Watch closel