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