Chocolate Pudding

1/2 cup white sugar
3 tablespoons unsweetened cocoa powder
1/4 cup cornstarch
1/8 teaspoon salt
2 3/4 cups milk
2 tablespoons butter

1 teaspoon vanilla

In a saucepan, stir together sugar, cocoa, cornstarch, and salt. Place over medium heat and stir in milk. Bring to a boil and cook, stirring constantly until the mixture thickens enough to coat the back of a metal spoon. Remove from heat and stir in butter and vanilla. Let cool briefly and serve warm, or chill in refrigerator until serving.