Microwave evaporated milk in a microwave-safe bowl at HIGH 2 minutes or until hot. Stir in crushed candies, stirring constantly until candies dissolve. Melt chocolate and butter in a large heavy saucepan over low heat, stirring constantly. Gradually stir in evaporated milk mixture. Gradually whisk in sugar. Cook, whisking constantly, over low heat 3 minutes or until smooth. Remove from heat, and whisk in salt.