- First, thread the marshmallows on a chopstick or skewer, and use a culinary torch to toast them to your liking. Set aside.
- Next, make the chocolate sauce (if you’re not using store-bought): combine all ingredients except the vanilla in a small sauce pan. Bring to a simmer while whisking constantly. Remove from the heat and stir in the chopped chocolate until melted. Stir in the vanilla, and then let cool completely.
- To make the milkshake: combine the marshmallows, ice cream, graham crackers and milk in a blender. Blend until mostly smooth. Let rest for a few minutes to soften the graham crackers.
- Meanwhile, drizzle chocolate sauce inside two 8-ounce serving glasses. Divide the milkshake between the two glasses.
- Serve, garnishing with extra marshmallows, if desired. You can also dunk the rim of the glass in chocolate syrup and then crushed graham cracker crumbs.
- Serve immediately.