Combine evaporated milk, powdered sugar, cocoa and butter in a heavy saucepan; cook over medium heat until mixture boils. Reduce heat, and simmer until mixture thickens. Remove from heat; stir in vanilla. Set aside to cool.
Combine chocolate cookie crumbs and melted butter, stirring well. Press crumb mixture into a 13"x9"x2" pan.
Cut ice cream crosswise into 1/2" thick slices. Arrange over crust. Spoon fudge sauce over ice cream; sprinkle with chopped peanuts. Cover and freeze until firm.
Let dessert stand at room temperature 5 minutes before serving. Yield: 15 servings.