Preheat oven to 175 degrees Celsius (350 degrees Fahrenheit) and apply non-stick coating to a standard donut pan.
In a large mixing bowl, whisk together flour, sugar, baking powder, nutmeg, and salt.
In a separate vessel, combine buttermilk, eggs, melted butter, and vanilla extract until fully emulsified.
Integrate the liquid mixture into the dry ingredients, stirring only until no dry streaks remain to avoid gluten over-development.
Transfer batter to a piping bag and fill each donut cavity to approximately two-thirds capacity.
Bake for 8 to 10 minutes or until the internal structure is set and a toothpick emerges clean.
Allow donuts to rest in the pan for 5 minutes before transferring to a cooling rack.
Combine powdered sugar, maple syrup, and milk in a shallow bowl, whisking until a smooth, homogenous glaze forms.
Submerge the superior surface of each warm donut into the glaze and place on a wire rack for the coating to stabilize.