1 can sweetened condensed milk
2 (1 oz.) sq. unsweetened chocolate
1/3 c. boiling water
2 tbsp. butter
1 tsp. vanilla

Heat milk and chocolate squares in top of double boiler until chocolate is melted and mixture thickens, stirring continuously. Add boiling water and continue cooking for 2 minutes. Remove from heat and add butter and vanilla; stir until smooth. Serve over vanilla ice cream. To reheat, add extra hot water as needed to produce desired consistency.