1 cup light brown sugar, packed 
1/3 cup milk 
1/4 cup light corn syrup 
1 tablespoon butter or margarine 
1/4 cup peanut butter 
vanilla ice cream, enough for 4 parfait glasses 
crushed peanut brittle or chopped peanuts 

In a medium saucepan over medium heat, combine brown sugar, milk, corn syrup, and butter. Cook, stirring constantly, until sugar dissolves and butter melts. Remove from heat. Add peanut butter and beat with mixer or whisk until smooth; let cool thoroughly. In parfait glasses, alternate layers of ice cream and cooled peanut butter sauce, beginning and ending with the ice cream. Top with crushed peanut brittle or chopped peanuts.