Start by preheating your oven to 350°F (175°C). In a bowl, mix together the flour, cocoa powder, baking soda, baking powder, brown sugar, granulated sugar, and sea salt. Whisk them thoroughly to ensure they’re combined.

In another bowl, beat the egg. Add the milk, sunflower oil, and vanilla extract. Whisk until it’s a smooth mixture, and everything is combined.

Pour the wet ingredients into the dry. Gently mix until barely combined. Do not overmix, or you might end up with tough donuts. Fold in the crushed Oreo cookies, allowing those delicious cookie bits to be distributed evenly throughout the batter.

With your batter ready, it’s time to fill your donut pan. Use a piping bag for precise filling or just a spoon. Fill each cavity about two-thirds full. This allows room for the donuts to rise without overflow.

Bake the donuts for approximately 10-12 minutes. They should spring back slightly when touched and pass the toothpick test. When they’re done, let them cool in the pan for a few minutes before transferring them to a wire rack.

While the donuts cool, prepare the glaze. In a bowl, whisk together powdered sugar, vanilla extract, milk, softened butter, and maple syrup until smooth. Then fold in the crushed Oreo pieces.

Once the donuts are completely cool, dip the tops into the glaze. Allow the extra glaze to drip off before placing them back on the wire rack. For an extra Oreo kick, sprinkle more crushed Oreo cookies over the glaze before it sets.