Chocolate Gravy

Source: Byrd Droppings

2 Tablespoons (heaping) cocoa
2 cups milk
1 3/4 cups sugar
2 Tablespoons (slightly rounded) flour
1 Teaspoon vanilla
Butter
shake of salt

Mix together all but milk in medium saucepan. Add enough milk to make paste. Stir in remaining milk (a little at a time) until smooth. Cook on medium until bubbling and gravy thickens. Stir in 1 teaspoon vanilla and a few pats of butter to taste.