Preheat the oven to 175C/350F and grease the donut pan lightly with butter.
Whisk together the flour, cocoa powder, sugar, salt, baking powder, baking soda, chocolate chips and set aside.
In a separate bowl, mix the oil, milk, egg, vinegar, vanilla and whisk to thoroughly combine.
Pour the wet ingredients into the dry and mix to combine.
Fill the donut pan 3/4 full and bake for 13m or until a toothpick comes out clean.
For the glaze: whisk together icing sugar, melted butter, vanilla and salt then stir in 1-2 tablespoons of milk, adding additional milk 1 teaspoon at a time until you get a glaze consistency.
Add food colouring a small amount at a time until you reach the desired colour.
If the glaze starts to set, heat it up briefly in the microwave.