Preheat your oven to 400°F (200°C). Butter and flour a 6-well doughnut pan.
In the bowl of a stand mixer fitted with the paddle attachment, combine granulated sugar, brown sugar, and the egg. Beat at medium speed until the mixture becomes light in color and well combined, approximately 1 to 2 minutes. Don't forget to pause and scrape down the sides of the bowl!
Next, add in the melted butter, vegetable oil, coconut extract, and vanilla extract. Beat this mixture at medium speed until everything is well incorporated, which should take about 1 minute.
In a separate small bowl, whisk together the cake flour, baking powder, and kosher salt. In another bowl, whisk the coconut milk with water until smooth.
With the mixer on medium-low speed, add the flour mixture to the sugar mixture. Alternate adding the coconut milk mixture, starting and ending with the flour mixture. Beat until everything is just combined; be careful not to overmix.
Spoon half of the batter (about 1 cup or 277 grams) into a large pastry bag. Cut a ½-inch opening in the tip. Pipe the batter evenly into the prepared doughnut wells, refilling the bag as necessary.
Tap the filled pan firmly on a kitchen towel-lined counter several times. This will settle the batter and help release any air bubbles that may have formed.
Bake the doughnuts in the preheated oven for 8 to 10 minutes. To check if they’re done, insert a wooden pick near the center; it should come out clean.
Allow the doughnuts to cool in the pan for 5 minutes. Then, carefully invert them onto a wire rack that’s placed over a parchment paper-lined baking sheet. Let them cool completely.
For the finishing touch, dip each doughnut halfway into the Coconut Glaze. Lift it straight out and swirl in a circular motion to let the excess glaze drip off. Place the glazed doughnut, glaze side up, on the wire rack.
Repeat the glazing process for all remaining doughnuts. If desired, garnish with toasted coconut flakes. Serve your Coconut Cake Doughnuts immediately and enjoy the tropical delight!
