Add glutinous rice flour, sugar, and cornstarch to a large bowl. Pour in the oil and milk, then whisk until the mixture is completely smooth and free of lumps.

Transfer the batter to a non-stick pan. Cook over low heat, stirring constantly with a silicone spatula to prevent sticking.

As the mixture heats, it will gradually thicken and come together. Keep stirring until a smooth, elastic dough forms and no longer sticks to the pan or spatula. Turn off the heat.

Remove the dough from the pan and gently stretch it a few times to improve elasticity.

Once cool enough to handle, roll the mochi into a log and cut into bite-sized pieces.

Toss the pieces in roasted soybean powder until evenly coated. Serve immediately.