Preheat the oven to 350°F and grease a donut pan with non-stick spray.

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

In a large bowl, mix together the melted butter, sugar, eggs, milk, sour cream, and vanilla.

Add the dry ingredients to the wet ingredients and mix until well combined.

Transfer the batter to a piping bag and pipe it into the prepared donut pan, filling each well three-quarters full.

Bake for 12 minutes or until a toothpick inserted into the center comes out clean.

Allow the donuts to cool in the pan for 2 minutes, then transfer them to a wire rack to cool completely.

In a double boiler over medium heat, melt the chocolate chips and coconut oil together until smooth.

Dip each cooled donut into the chocolate glaze, then return them to the wire rack.

Place the glazed donuts in the fridge to allow the glaze to set.

Sprinkle chocolate shavings over the top of each donut before serving.