• Preheat oven to 325 F and spray a 6-cavity donut pan with non-stick cooking spray.
• In a large bowl, sift together the dry ingredients (flour, sugar, baking powder, baking soda, salt, and nutmeg).
• Add the wet ingredients (buttermilk, egg, vanilla, and oil) to the flour mixture. Stir to combine.
• Put donut batter in a disposable piping bag. Pipe donut batter into the cavities of the donut pan. Alternatively, carefully spoon batter into the cavities.
• Bake 12 to 14 minutes until the donuts are golden brown and spring back when gently pressed.
• Let cool for 5 minutes in the pan, then turn out onto a wire rack to fully cool.

Meanwhile, make the glaze:

• Place the butter in a small microwave-safe bowl. Microwave in 20-second bursts until melted.
• In a shallow, medium bowl, combine combine confectioners' sugar, corn syrup, melted butter, and vanilla extract. Gradually add just enough milk until a thick glaze forms.
• Dip each donut in the glaze, then top with sprinkles.
• Leftover donuts can be stored at room temperature in an airtight container for several days.