Combine sugar, water, corn syrup and salt in a 2-qt. heavy saucepan. Place over low to medium heat and stir until sugar is dissolved, then cook to the soft ball stage (234 to 236°).
Remove from heat; add marshmallows and stir until melted. Add flavoring and nuts, stirring only until well combined.
Drop by teaspoonfuls onto waxed paper. If mixture starts