Soft, cakey baked donuts with a classic nutmeg-kissed crumb, finished with a rich, glossy chocolate glaze and plenty of sprinkles for a nostalgic donut shop bite at home.
Preheat oven to 350°F (177°C). Grease a donut pan; this recipe makes 8 donuts, so prepare a second pan or plan to bake in batches.
Whisk dry ingredients in a large bowl: flour, baking powder, baking soda, salt, and nutmeg.
In a medium bowl, whisk wet ingredients: egg, brown sugar, milk, and sour cream or yogurt until smooth. Whisk in melted butter and vanilla until fully combined.
Pour wet ingredients into dry ingredients and stir just until combined; do not overmix. Batter will be thick.
Transfer batter to a piping bag or a zip-top bag with a corner snipped. Pipe into donut cavities, filling each about 1/2–2/3 full.
Bake 9–10 minutes, or until donuts spring back when lightly pressed.
Cool in the pan on a rack for 2 minutes, then remove donuts to the rack to cool slightly. Re-grease the pan and bake remaining batter if needed.
Make the chocolate glaze: In a microwave-safe bowl, combine chocolate chips, butter, corn syrup, and water. Microwave in 20-second increments, stirring after each, until melted and smooth.
Dip the tops of slightly cooled donuts into the glaze. Add sprinkles if desired and let the glaze set.
Serve fresh. Donuts are best the same day; leftovers keep about 2 days or freeze for longer storage.