Preheat the oven to 375°F (190°C). Lightly grease your baking dish or skillet, or line it with parchment.
Make the Oreo base: Crush about two-thirds of the Oreos into coarse crumbs.
Mix with melted butter and a pinch of salt. Press this mixture into the bottom of the pan to form a loose crust. It doesn’t need to be perfect—rustic is fine.
Add chocolate: Scatter chocolate chips or chopped chocolate evenly over the Oreo base.
Aim for a generous, even layer so every scoop is gooey.
Top with marshmallows: Cover the chocolate with mini marshmallows. Pack them in close so you get a toasty, golden lid.
Finish with Oreo pieces: Break the remaining Oreos into chunks and sprinkle over the top. This adds a crunchy bite and looks great.
Bake for 8–12 minutes, until the marshmallows are puffed and golden-brown and the chocolate is melted.
Optional broil: For extra toast, switch to broil for 30–60 seconds.
Watch closely—marshmallows burn fast.
Cool slightly: Let it sit 3–5 minutes so it sets up a bit but stays molten inside.
Serve warm with your favorite dippers. Scoop from the edge so you get a little of everything in each bite.