Whisk milk, brown sugar, egg, cocoa and cornstarch in a medium saucepan. Cook over medium-low heat, whisking constantly, until the mixture bubbles and thickens, 3 to 5 minutes.
Add chocolate chips and vanilla; stir until the chips have melted. Transfer the pudding to a bowl and cover with wax paper to prevent a skin from forming. Refrigerate until you are ready to serve it.
1 fat-free milk, 2 other carbohydrate