Preheat the oven. Set your oven to 400°F (200°C). If you’re using a cast-iron skillet or oven-safe baking dish (8- or 9-inch), lightly grease it to prevent sticking.

Layer the chocolate. Pour the chocolate chips into the bottom of your skillet or dish. If using, drizzle 1–2 tablespoons of milk or cream over the chips and add a tiny pinch of salt for flavor depth.

Add the marshmallows. Arrange marshmallows in a single layer on top of the chocolate. Pack them snugly so they toast evenly. Mini marshmallows cover more evenly, but regular ones work great too.

Bake until melty and golden. Place the dish on the center rack and bake for 7–10 minutes. Keep a close eye on it starting at the 6-minute mark. You want deeply golden, toasted tops and fully melted chocolate underneath.

Rest briefly. Remove from the oven and let it sit for about 2 minutes. This helps the chocolate set just enough so it’s scoopable rather than soupy.

Serve immediately. Bring it to the table hot with graham crackers and any other dippers. Scoop from the edge and swirl marshmallow and chocolate together with each dip.