In a mixing bowl, whisk together the glutinous rice flour, cornstarch, cocoa powder, white sugar, corn oil, and milk until smooth and well combined.

Pour the prepared batter through a fine sieve into a heavy-bottomed pot to remove any clumps.

Place the pot over low heat and stir continuously for about 10-15 minutes until the batter thickens significantly.

Transfer the thickened batter to a cornstarch-lined surface and let it cool for about 10 minutes.

Divide the mochi dough into small portions and roll each into uniform balls.

Crush the Oreo cookies into fine crumbs and roll each mochi ball in the crumbs until fully coated.