Preheat your oven to 350 degrees F. Lightly spray a 6-cavity donut pan with non-stick cooking spray. This recipe yields about 8 donuts, so if you have two pans, spray both; otherwise, bake in two batches.

In a large bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.

In a separate bowl, whisk the egg, brown sugar, granulated sugar, melted butter, instant coffee powder, vanilla extract, peppermint extract, and buttermilk until smooth and no lumps of brown sugar remain.

Using a rubber spatula or wooden spoon, gently fold the wet mixture into the dry ingredients until just combined. Do not overmix; the batter should be thick.

Carefully spoon the batter into the prepared donut pan, filling each cavity about 1/2 to 2/3 full. Alternatively, transfer the batter to a zip-top bag, snip off a bottom corner, and pipe it into the pan.

Bake for 8 to 10 minutes, until the donuts spring back slightly when touched. Let them cool in the pan for 5 to 10 minutes, then transfer to a wire rack to cool completely.

While the donuts cool, prepare the glaze. In a small microwave-safe bowl, combine the chocolate chips, corn syrup, butter, milk, and instant coffee powder. Microwave in 15- to 20-second bursts, stirring after each, until the chocolate is almost melted. Be careful not to overheat, or the chocolate may seize.

Remove from the microwave and whisk until smooth and glossy. Dip the top of each cooled donut into the glaze, allowing any excess to drip off.

Immediately sprinkle crushed candy canes over the wet glaze. Let the glaze set at room temperature for about 10 minutes before serving.