Step 1: Create the Toasted Marshmallow Syrup
Spread the 1 cup of mini marshmallows in a single layer on a heatproof plate or baking sheet. Using a kitchen torch, toast the marshmallows until they are deeply golden brown and smoky, turning them for even color. Alternatively, you can place them under a preheated broiler for 30-60 seconds, watching closely to prevent burning. In a small saucepan, combine the water and granulated sugar. Heat over medium, stirring, until the sugar dissolves. Add the toasted marshmallows to the simple syrup. They will melt and swirl into the liquid. Continue to stir over low heat until completely smooth. Remove from heat, stir in the vanilla and salt, and let cool completely. Strain through a fine-mesh sieve if any unmelted bits remain.

Step 2: Prepare the Cold Brew Concentrate
Combine the coarsely ground coffee and cold water in a large jar. Stir to ensure all grounds are saturated. Cover and steep at room temperature for 12-24 hours. Strain through a fine-mesh sieve lined with a coffee filter into a clean container. Refrigerate until ready to use.

Step 3: Whip the Marshmallow Cream Cold Foam
In a tall, chilled bowl or measuring cup, combine the cold heavy cream, cold milk, 2 tablespoons of the cooled toasted marshmallow syrup, and the marshmallow fluff (if using). Using a handheld milk frother or a whisk, whip the mixture until it becomes thick, frothy, and holds soft peaks. It should be pourable but luxuriously dense. Do not overwhip into stiff peaks.

Step 4: Assemble the Drink
Take a tall glass and add 2-3 tablespoons of the toasted marshmallow syrup. Fill the glass to the brim with fresh ice cubes. Pour the cold brew concentrate over the ice, leaving about 1.5 inches of space at the top.

Step 5: Top with the Marshmallow Foam
Slowly and deliberately pour the marshmallow cream foam over the back of a spoon held just above the surface of the coffee. This technique is crucial for allowing the dense, sweet foam to float on top, creating a distinct and beautiful layered effect.

Step 6: The Final Toasted Garnish
Place a small cluster of additional mini marshmallows directly on top of the foam. Carefully use your kitchen torch to toast them until they are golden brown, bubbly, and slightly charred. This final step adds an authentic campfire aroma and a spectacular visual finish.

Step 7: Serve and Savor
Serve immediately with a straw and a spoon. The joy is in the first sip—through the layer of warm, toasted marshmallow and cool, creamy foam, down to the strong, sweetened coffee below. Encourage drinking it unstirred initially to experience the layers, then mixed for a unified flavor.