2(1 oz) squares unsweetened chocolate
4 tbsp butter
2 cups sugar
2 (5 oz) cans evaporated milk (equals 20 Tbsp if using from a large can)
2 tsp vanilla
Melt the chocolate and butter together in a large saucepan over low heat. Stir in the sugar until well combined. Add the evaporated milk and increase the heat. Cook rapidly and bring to a rolling boil, stirring constantly. Boil for 2 minutes, stirring constantly. Remove from heat and stir in the vanilla. Cool completely and store in the refrigerator.
Serve warm or cold.