Prep your steamer setup: Place a stand or ring inside a large pot or deep pan. Add about 1.5 inches of water. Cover with a lid and bring to a gentle simmer over medium heat while you prepare the batter. If using a pressure cooker, remove the whistle/weight.

Prepare the cake pan: Grease a 6- or 7-inch round pan (or any small heatproof tin) with oil or butter. Line the bottom with parchment for easy release. Set aside.

Crush the Oreos: Add Oreos to a blender or food processor and blend to a fine powder. You can also put them in a zip-top bag and crush with a rolling pin until sandy with minimal lumps.

Make the dry mix: In a mixing bowl, combine the crushed Oreos, baking powder, baking soda, sugar (if using), and a pinch of salt. Stir to distribute evenly.

Add wet ingredients: Pour in the milk gradually while whisking to avoid lumps. Add vanilla and the oil or melted butter. You want a thick, pourable batter—similar to pancake batter. If it’s too thick, add 1–2 tablespoons more milk.

Rest briefly: Let the batter sit for 2–3 minutes to hydrate. This helps the texture.

Pour and tap: Transfer the batter to the prepared pan. Tap the pan on the counter a few times to pop large air bubbles and level the surface.

Steam the cake: Carefully place the pan onto the stand inside your preheated pot. Cover with a tight lid. Steam on medium-low heat for 30–40 minutes. Avoid high heat to prevent cracking or a rubbery texture.

Check for doneness: Insert a toothpick in the center at the 30-minute mark. If it comes out clean or with a few moist crumbs, it’s done. If there’s wet batter, steam for 5–10 more minutes and check again.

Cool and unmold: Turn off the heat. Let the cake rest in the pan for 10–15 minutes. Run a knife around the edge, then invert onto a plate or rack. Peel off the parchment.

Optional ganache topping: Warm the cream or milk until hot (not boiling). Pour over chocolate chips and rest for 1–2 minutes. Stir until smooth. Spread over the cooled cake and sprinkle with crushed Oreos.

Slice and serve: For neat slices, let the cake cool completely or chill briefly before cutting.