1/2 cup butter or margarine
2/3 cup unsweetened cocoa powder
1/3 cup granulated sugar
1 (14 ounce) can sweetened condensed milk
1 1/2 teaspoons vanilla extract
In a saucepan, melt butter over low heat. Stir in cocoa and sugar. Add sweetened condensed milk. Cook, stirring constantly, until sugar is dissolved and mixture is smooth. Remove from heat. Stir in vanilla.