Combine sugar [1cup], cocoa powder [1/4 cup], and flour [1/4 cup] and stir until no lumps remain.
Combine the milk [2 cups] with the cocoa mixture in a saucepan or deep skillet and set over medium-high heat.
Whisk and stir until mixture starts to barely bubble and thicken.
Reduce heat and continue to cook and stir until desired consistency is reached.
Remove from the heat and stir in the butter [3 tablespoons].
Leftovers can be stored in the refrigerator for up to 3 days. Reheat in the microwave for 45 to 60 seconds or heat in a small pan set to low heat, stirring constantly until heated through.Nutritional data provided for reference only and is for chocolate gravy only.