Preheat your oven to 350°F (175°C) or heat oil if frying.
In a bowl, combine the flour, sugar, baking powder, and salt.
Whisk together milk, eggs, and melted butter. Combine with dry mix.
Pour the batter into a doughnut pan and bake for 12–15 minutes, or fry until golden brown. Cool on a rack.
Prepare the icing by mixing icing sugar with a splash of milk until smooth. Divide into four bowls and add food coloring.
Decorate by house: Gryffindor: red icing with caramel crumbs or gold sprinkles; Slytherin: green icing with crushed chocolate cookies; Ravenclaw: blue icing with silver sprinkles; Hufflepuff: yellow icing with honeycomb or cookie pieces.
Let icing set before serving.
