Preheat and prep: Heat your oven to 350°F (175°C). Lightly grease a standard 6-cavity donut pan. If you have two pans, even better.

Mix the dry ingredients: In a medium bowl, whisk 1 cup flour, 1/3 cup cocoa powder, 1/2 cup sugar, 1 teaspoon baking powder, 1/4 teaspoon baking soda, and 1/4 teaspoon salt. Break up any cocoa lumps.

Whisk the wet ingredients: In another bowl, whisk 1 large egg, 1/2 cup milk, 1/4 cup yogurt or sour cream, 2 tablespoons neutral oil, and 1 teaspoon vanilla until smooth.

Combine gently: Pour the wet mixture into the dry. Stir with a spatula just until no dry streaks remain. Do not overmix; a few small lumps are fine.

Fill the pan: Spoon batter into a piping bag or zip-top bag and snip the corner. Pipe batter into the donut wells, filling each about 3/4 full for a nice rise.

Bake: Bake 9–12 minutes, until the donuts spring back lightly when touched and a toothpick comes out with a few moist crumbs.

Cool: Let donuts cool in the pan 5 minutes. Turn out onto a rack to finish cooling completely. Glazing warm donuts can melt the glaze too much.

Make the chocolate glaze: In a small heatproof bowl, combine 1/2 cup semisweet chocolate chips, 2 tablespoons butter, 1/2 cup powdered sugar, and 2 tablespoons milk. Microwave in 20–30 second bursts, stirring between each, until smooth and glossy. If too thick, add milk by the teaspoon; if too thin, whisk in a little more powdered sugar.

Dip and decorate: Dip the top of each cooled donut into the glaze, let excess drip, then place on a rack. Immediately add sprinkles before the glaze starts to set.

Set and serve: Let the glaze set 15–20 minutes. Enjoy fresh, or store as directed below.