Brew the coffee. If making cold brew at home, combine 1 cup coarsely ground coffee with 4 cups cold water. Stir, cover, and steep 12–18 hours in the fridge. Strain through a fine mesh or coffee filter. You’ll have a smooth concentrate ready for mixing.

Toast the marshmallows (optional but worth it). Set marshmallows on a parchment-lined tray. Use a kitchen torch to lightly toast them until golden, or broil on high for 30–60 seconds, watching closely. Toasting deepens the marshmallow flavor and adds a subtle caramel note.

Make marshmallow syrup. In a small saucepan, combine water and sugar over medium heat. Stir until the sugar dissolves and simmers. Add the marshmallows and stir until melted and smooth. Remove from heat, add vanilla and a pinch of salt, and let it cool. The syrup will thicken slightly as it rests.

Whip the cream. In a chilled bowl, whip heavy cream to soft peaks. Fold in 1–2 tablespoons of the cooled marshmallow syrup for flavor. You’re aiming for a fluffy topping that still pours slowly.

Build the drink. Fill a tall glass with ice. Add 1/2–1 ounce of marshmallow syrup (start small; it’s sweet). Pour in 1/2 cup cold brew concentrate and 1/2 cup milk. Stir gently to combine and taste. Adjust with more syrup or more coffee as needed.

Top and finish. Spoon or pour the marshmallow whipped cream over the drink. Sprinkle with graham cracker crumbs or a dusting of cocoa powder if you like a s’mores vibe.

Serve. Add a straw and give it a quick stir as you sip so the cream swirls into the coffee. It should be sweet, creamy, and still clearly coffee.